Another easy boss would be Rubicante from Final Fantasy IV

Haven't played them all yet, so don't quote me on this, but the easiest final boss fight for me was the Undying from XII.  I finished him off on the first try.  All you have to do is keep attack, no fancy magic or quickenings needed to win.  Of course using them speeds up the battle, but it can be won with out them. 
The easiest general boss fight is Lugae from IV. He's all timing your attacks and dumping elixirs on him. Serious waste of elixirs.

If you've played Final Fantasy VI, then let's talk about the Phantom Train. You can kill this thing instantly with a tuft of Phoenix Down. ONE. PHOENIX. DOWN.

I'd say everything in the first final fantasy was easy...well
I did have my upgrades as soon as i could get them i was also...40 levels over leveled i even had max level by the final battle

I think the easiest boss I've faced so far would be Ifrit from the beginning of Final Fantasy 8. I literally one-shot killed him with summoning Shiva, who I had trained rather excessively and already had Summoning Magic +30%/20%/10%. I know, overkill.

The easiest boss I've ever faced and I think some people will agree with me, was Phantom Train in FF6. All it took was a phoenix down XD

The easiest boss I've fought was the first boss in Final Fantasy 3. You just have to use ice against it. Like use the ice item 3-5 times and he's dead

Probably Ultros from Final Fantasy VI on the SNES

I don't know if you would consider this a boss, but the easiest boss i faught was myself in Final Fantasy 4, it was way to easy i didn't even much have to do anything but slash him about 5 times and he was dead thats how strong i was.

The easiest boss... could be...??? Yeah! Garland you WON! He is very easy if you have your party +level 3. And he only attack... really?

Well the first boss in any game is usually the easiest... considering you don't have a lot of resources and they're just introducing you to the game... they usually make your first real boss fight pretty hard to fail.

As for a final boss... I guess I had the easiest time of that in Final Fantasy 5? At least, I don't recall struggling too much there.

Any other easy boss battles come from Final Fantasy 4. Paladin Cecil fighting Dark Knight Cecil is just a matter of defending until it's over... and just about every significant boss battle had a gimmick to easily exploit (particularly the Fiends) which made these super easy to beat. I actually find the RANDOM battles more challenging than the boss battles in that game.

Hm personally, I think the ghost one in Cosmo Canyon, Final Fantasy VII, the one with two flames is the easiest one, even though I didn't know the trick to defeat that one... It's one of those bosses where you just phoenix down them to death, like the one in the Ice area in Final Fantasy VIII, the one before Esthar City. Both amazing games, by the way.

DarthDub : That is where your wrong actually, in FFVIII the bosses leveled up with you, making it nearly impossible to overlevel and wipe out the enemies

But back on topic, the easiest boss? hmmm.... I've played all the bosses..... Phantom Train, because of the cheap trick you could do with the Phoenix Down

Easiest normal Boss: Garland (FF1)
Easiest Final Boss: Chaos (FF1)

Ultros from Final Fantasy 6.
Gogo is another that comes to mind.
But I have to go with Ultros. Merely because you meet him repeatedly. The fight that was the easiest would have to be the "opera house" section.

I am sure there are easier boss fights.
I am partial to Ultros.

Good Luck To All.
I'm done. Stick a fork in me.
Peace.

Definitely the Phantom Train from Final Fantasy VI. As stated before, you can kill it with one phoenix down!

In FF1, I found all fights to be mainly easy, with Taimat being the hardest for me(Not sure why) But I would like to say that Chaos, at the end, is actually Garland(Some people are saying it like they are two different people, when in fact, After the light warriors kill him, he says that he will just be returned to the past as Garland, and when he dies from there, he regains all his memories and becomes an even stronger challenge for the light warriors) As for the easiest, I guess Lich was pretty easy for me.....NO! The Pirate and his men! Just cast sleep on them, and they can't fight till they get hit or somehow wake up, then just hit them with another sleep spell.

FF2, the easiest fight for me was against the general that was protecting the mythril(Cause at this time, I am already able to kill the gold armored ones in the castle. Amazing things are capable when you have Mindu....minwu? However you pronounce his name, in your party casting uber powerful white magic)

FF3, The one with the Onion kids, not FF6 with Terra, I only got a few bosses in, literally the first and second boss, and then I get tired with how slow it moves. The first boss being the turtle looking thing(I believe admantiose in other games, but less powerful)

FF4, I did not like this game. Every fight annoyed me, not that it was hard, but that something about the characters just didn't sit right with me. Cecil, a dark night who turns paladin(Though the two are completely different fighting groups, believing completely different things) all the way to the hateful Kain who SOMEHOW fights off a mind control spell long enough to pull himself out of the fighting so his ARCH RIVAL can take all the glory..........Yeah, the only thing I liked was Rydia, and how she magically grows up in the time altering zone of the pit of some things stomach. As for the easiest fight, had to be Cecil's fight with himself. 

FF5, hands down, the easiest fight was with the Mime. You literally had to sit there for...what? A minute? Then he says something along the lines of, you can be like me without my power, here you go!

FF6. I LOVED this game. It was my favorite till 7 came out(And I played it as the misplaced title FF3) I loved every fight(Unlike FF4) and every fight seemed to bring me a new challenge to overcome. However, the first time I played it......I got stuck at the part when you get Sabin. I just couldn't figure out what keys I was supposed to push to use his blitz. After a bit of looking around, I decided.....THATS FREAKING EASY!

FF7. Assuming you were like me when I first played FF7, and ran from virtually every fight, then you would find that all the boss fights were hard(And back then, I didn't take the side paths to get more bosses and story line) but I found that, with Vincent's....I believe, Limit 3, EVERYTHING was easy. He almost literally couldn't die(Again, I think it was limit 3 but I could be wrong) So I found all fights easy after I got Vincent(Though getting him was a major pain in my.....but) But without Vincent, I would have to say the monster in the sewers who continually cast Tsunami. If you were lucky, you could start that fight with full health, leave the room, and make yourself a sandwich, come back, and he was dead, and your characters weak, but still alive.

FF8, Another one that took me a while to get into. I didn't really like the Draw system until I realized that I could get some pretty advanced spells fairly early on(Siren had to be my ultimate favorite GF in the beginning) But as far as easy bosses, I found the easiest to be the Ifrit fight. You really didn't need to use your GFs on him, you could just swing at him and beat him in the 10 minute limit(And that's without pushing R2 to get the special shot added to Squall's attack), but if you wanted to get him beat quick, then Shiva was the way to go, since he shouts out, SHIVA! THEY HAVE SHIVA!, and the damage could rack up to(If you had leveled as much as I had) up to the thousands, and beat him in one to two hits(if you just used Shiva, not the thunder bird who's name is hard to pronounce but is a reference to an Indian god of thunder)

FF9, Again, up to this point, FF7 was my favorite. But with FF9, a new favorite was born. I loved everything about this instalment, from the new level up system(Loved that you had to gain AP for your skills, and XP for your level). As for easiest fights, I found that none were to easy, since I always wanted ALL the items that the bosses had on hand for my sticky fingers to grab at. By the time that I was done with them, they would literally be wearing nothing if the game was "Anatomically correct"....probably creepy to admit, and good thing it wasn't. But aside from the thieving, I liked the Ant lion fight best, and found it oddly simple(Didn't like the evil forest fights at all, cause I had to use my hard earned potions on idiot Garnett/Dagger....WHOS A FREAKING WHITE MAGE! Seriously, why couldn't she heal herself? And ViVi, who was a FREAKING BLACK MAGE! Seriously, why didn't he burn his way out of the VINE CAGE!!!!!!!!!! VIVI, USE FLAMETHROWER!!!!!!!! SUPER EFFECTIVE!!!!!!!!)

For regular bosses I would have to say the magitek armors that kefka send after you in the desert. just use noiseblaster and thats it. for final boss, I would say kuja/ necron. even combined those two are so easy even without the extremely broken in that game auto regen.

The easiest final boss is Yu Yevon. I mean, come one, auto resurect? And generally speaking, any boss is a breeze once you get the Magus Sisters.

In FF 7, any non-Weapon boss (except Sephiroth) is easy with Knights of the Round Table. I killed Jenova Absolute with only one hit.

In FF 8, once Squall gets high enough strength AND has a lot of aura, he becomes a killing machine. Ultemecia was so easy (of course, I had a few megaelixirs)

In FF 2 (origins, at least), the final boss is super easy with a pair of blood swords.