I know what you're thinking. Predators? What is this? Well, I'm going to make a list on what characters can beat other characters easily. This is a work in progress.
Cable: no one really uses him anyway but if I were to choose, Cap, Magneto and Thor.
Dr. Strange: touchy, because it's hard. If he's blaster: a tact Strange will do the job nicely. If he's tact, Psylocke, Gambit, Spiderman, Black Panther, even Black Cat.
Havok: another rare one, Black Panther can rape him, Emma Frost, Cap, Mockingbird.
Human Torch: Tact Strange, Emma Frost, Black Panther, Hawkeye, Mockingbird.
Iron Man: now a rare one, Black Panther, Emma Frost, Scarlet Witch, Black Widow, Wolverine.
Ms. Marvel: Havok (but you will need assistance), Emma Frost, Mockingibrd, Gambit, Ghost Rider.
Phoenix: Super Annoying!: Gambit, Black Panther, Black Widow, Mockingbird, Valkyrie, Hulk, Hercules, Thor (the last three, you will need someone to kill Phoenix again)
Scarlet Witch: (Super Touchy): Emma Frost, Tact Strange, Mod. Sif (Scrapper, if you care), Thor, Cap.
Storm: Black Panther (they'll be getting a divorce soon), Emma Frost, Scarlet.
Black Panther: make sure you have no blasters (and if you do, PROTECT), Gambit, Black Widow, Spiderman, Kitty Pryde.
Cap: might be disagreement: Gambit, Black Widow, Spiderman, Emma Frost, Thor, Hercules
Cyclops: why use him when you've got Cap?: Tact Strange (if he's blaster), Psylocke, Gambit, Black Cat
Emma Frost: ah....the creme de la creme..AND A PAIN IN THE NECK: Gambit, Black Widow, Thor, Valkyrie, Mod. Sif
Hawkeye: really?: Black Widow, Gambit, Kitty Pryde, Spiderman, Thor, Hercules, Mockingbird
Magneto: this guy kinda doesn't do anything. He does Heavy Metal the entire time (and it has a 3 round cooldown), so as of now (2/17/13), anyone. Except Emma.
Mr. F: the rarest of the F4: Wasp, Tact Strange, Tact Iron Man, Tact Storm, almost anyone with good acc and uses energy moves
War Machine: really someone you'll see if you're a low level, although he may be buffed again: Invisible Woman, Spiderman, Psylocke, Emma, Herc, Colossus.
Black Cat: not someone you'll see very often, but be cautious, claws outfit + stroke of luck can mess your day up: Thor, Hercules, Luke Cage, Colossus,
Black Widow: hard to kill: you guys suggest these, I'm out of ideas. Sorry for any inconvenience.
Gambit: Hulk, Iron Fist, Black Widow
Invisible Woman: Blas Strange,