This is the first of the expansion week and like Combat Villain before it, it falls on Thursday so you can play it twice on the same day after reset, making it also important for score purposes to have a solid team. Sadly, this day like others in the expansion week have a small pool of characters to choose from.
Probably you're 2 biggest contenders are Stryfe and Magneto. Both do require a heavy investment in order to obtain, but I think they're the best. Baron Mordo, Enchantress, Malekith, Kaecilius, Lash, Mysterio, Red Skull, and Whiplash are all underwhelming. At least Lash's leadership can be useful if you need it.
Ulysses Klaue is pretty good to go over 100k, and gives a crit damage buff to the team at T2. Building him as a damage dealer at first and support later is acutally a pretty good stategy.
Yellowjacket at T2 will do good damage, but since mine is not T2 I can't really give an accurate estimation of his power.
Cyclops' uniform from Age of Apocalyse also makes him a villain and brings him as a solid support or damage dealer as well. I haven't played him as a main damage dealer yet, but I think he can do 100k. Stay tuned. He does have good team ups with the other mutants I mentioned above and gives off a team wide attack boost at T2. I usually use him instead of T2 Klaue as the support character.
Magneto - I haven't tried him in this mode since the new update so I don't have him T3 or with a uniform or anything. I used him at T2 with his own leadership, Cyclops and Klaue. My build is nothing special: no uru, 4* power of Angry Hulk, and a defensive obelisk not worth mentioning since it buffs nothing. I scored about 202k with him with rotation of 4-2-5-1-3. Probably not optimal. I'll update this later when I test out the uniform.
Stryfe seems to be the best damage dealer in this mode (T3 Magneto nonwithstanding). Mine is still level 60, gear 20. All skills are at 6 and he has no uru. He has a partially awakened power of angry hulk set and a 3* filler obelisk with crit damage 26%, all defense, and increased damage by 130%. Not great but decent.
I use a rotation of 2c-4c-3-5. He creates a lot of lag in my phone with all the animations, but if you're careful you can still do well. His 3 skill is channeling, but you can move during the animation to keep dodging meteors. The increased damage should land on the 3 during each rotation. The team I've been using is Magneto's leadership, Cyclops, and Stryfe. I scored only about 330k with this team, but with a stronger build he can definitely go higher than that.