(Keep note that I like to incorporate both min/max and character concept)
Paroxysm Zero is my DM/Fire. He's a rival of my DM/Inv Scrapper. I know Dark Melee is really supposed to be for the arcane types, but the way I saw it (given my Spidey fandom), a lot of the powers from DM could fit a symbiote type.
Long story short behind Paro Zero is (and yes, he's a lot like Carnage) basically, he was a low ranking member of the Hellions, who just loved arson. I pretended Crey had a new symbiotic program which is fusing biological/chemical materials with salvaged alien technology. When Crey found out about this thug's history (it's what he did to my Scrapper, you'd have to read his background; a grudge, if you will), they offered him to be part of their symbiotic program. He gladly accepted, as long as it met his needs for lighting everything on fire. His mindset grafted with the symbiote perfectly and now, in addition to the regular powers of the symbiote (regeneration, additional strength, tendrils that can drain life or incapacitate...), he is an incarnate of what he loves to do best.
And in terms of gameplay, I love the 2 heals and 2 end recoveries. I always duo him with my friend who is a AR/Thermal Corruptor. The shields just make him unstoppable, hehe.