Emma Frost - Ignore her til the end. Her attacks are mostly annoying with Stun and Pseudo-Stun Psychic Tap (since either you must use a buff or recharge to ignore the big damage). With all three heroes concentrating on her, the dreaded Diamond Body doesn't always reduce the damage to miniscule amounts.
Phoenix Five Emma Frost - The bane of my existance...because of how often Cosmic Power, Unlock Potential, and War Diamond nullifies my strategy right now, I use fauleater on her while either using buffs or recharging my heroes. When they attack, it almost always takes away the burning and biofeedback debuffs so I don't even have them trigger her diamond body effect.
Human Torch - A tactician hero, a target spotter, goblin glider. It deals deadly crits as well as extra damage against flyers, plus the spotter (unfortunately all I have now is target painter) adds to the crit hit. I can usually knock him out in one or two attacks (one turn!) The only annoying part is if he uses Blazing Speed because Goblin Glider is a ranged attack.