I don't think Megatron needs to breathe though, on account of him being in space multiple times. As for fire damage, it will only protect against so much, and Megatron's cannon has to do a lot.

Megatron is just going to think the fighter is an insect and the fighter will just think Megatron is an equally pathetic Iron golem, so they're both surprised.

Edit: Megatron is wily however, whereas an optimized, generic fighter doesn't usually have a lot of intelligence,.

Slashing Megatron's throat...yeah, that'll do alot...

Anyways, Megatron grabs Fighter in the air, then smooshes him between his fingers, then drops him on the ground and commences stomping.

And if this Fighter can't be caught, why post the battle?

While the fire resistance might stop fire damage dealt by Megatron, will it stop the force of his lasers from pushing the fighter down the ground, or ripping him a new hole? All fire resistance does it prevent the flame damage dealt by fire, but not the actual physical force of the beam flying at him and hitting him. I'm easily throwing my money at Megatron here.

Plus the fact that even an extraordinarily tall man is still barely taller than the barrel of the gun...

hmmm..........what kind of shield does the fighter have?

Even Hasted, a fighter isn't going to be avoiding beams of light that Megatron is shooting.

He wouldn't be moving faster than the beams of light, he would be moving faster than the muscles (or motors) aiming them...........and I think the beams of light you're referring to are commonly called "lasers"

*activates traditional 'I shoot you 60000 times, and after a cloud of dust, you aren't hit at all' cliché that is so rampant in transformers... with similar giant robots.*

with aim like that, the fighter would take down Megatron fairly easily.......

Nah, Fighter can't really put his sword through the Alloy that Megatron is made out of. He's not exactly the most agile man in the world. I'd bet more on Thief if he had the strength of fighter, as Megatron's 'hit someone when he's on you like a little rat' skill is quite low.