Mutagen Men...
 

I honestly don't know who to pick.

IDW; Seymour Gutz has PATHOS.

Mutagen Man only appeared once and was apparently cured in the 1987 cartoon so he did not get much time to flesh out his character (pun unintended). Yet he is an ongoing character in IDW with elements that the 1987 cartoon introduced so I will go with IDW. Nick's version? He was Zach then Zach was turned into Mutagen Man out of his own stupidity. He is dormant in Donatello's lab and the plot needs resolution so he can be properly forgotten about not keeping us waiting to get it over with.

IDW, absolutely. Best design, most tragic backstory, he's great.

The OT Mutagen Man was a tragic victim of Shredder and he almost killed April in the most gruesome way in the series. Seriously, he had April dangling on a rope being pulled directly into spinning gears and spikes. She would have been slashed and grinded to a pulp.

It was like something out of a torture anime.

Isn't the classic toy backstory the most tragic? That should be an option. I choose Playmates toyline Mutagen Man.

I'd have to go with the IDW Mutagen Man, the dude is so miserable he thought the only rescue there was for him was a bullet in the brain.

http://1.bp.blogspot.com/-cwOyFvo14H.../s1600/1-4.png

I'll give it to Seymour as well, but to be fair he and Timothy are the only versions I have any real experience with. Never had the toy, never saw the Fred Wolf... for the longest time only knew of him from the name.

I don't think you're missing much by not watching the one episode he's in, he's a wimpy nerd who is less concerned with his horrific transformation itself than how it will hinder his job. I'm not joking, he's a mailman who has to deliver a letter and even though he dislikes being a jar of guts, his main reason for wanting to turn back is so he can continue delivering mail.

IDW. The other two don't even come close.

The OT Mutagen Man also had shape-shifting powers, which none of the other two have.

Yeah, that sounds like that show. :)

Zach was never that annoying. At least Zach used his skill to find the Turtles and would've been the type to actually train and stuff in the situation.

Timothy was just straight up annoying from the start.