Marvel Super Hero Squad: The Infinity Gauntlet

There is only one feat named 2099 COSTUME that Dr. Doom owned.
The condition is defeat 50 enemies with Dr. Doom's heroic attack.

My suggestion is as follows:
1.Choose Challenge mode.
2.Choose Dr. Doom as your Hero.
3.Choose Survival mode.
4.Choose NO.5 named CONSTRUCTION SITE due to another achievement named "Fear the might of Doom?" which is defeat 50 doombots. So you can solve two achievements at the same time.
5.After defeat couple doombots in the begining, you will have the heroic attack to shock several emenies at once(8 kills for 1 attack from my record).
6.After 10 mins, both of the achievements will be unlock.

This achievement is really easy. Goto Freeplay. Select level "Rhythm of Olympus". You will start with Thor & Falcon. Use them until you get to the dummy arena. Switch to Dr. Doom, block and defeat the 3 rotating dummies. Then you will have to do a charge attack on 3 dummies with shields. Then 8 more rotating dummies will come in, but you will have earned a heroic attack by now. Simply use it, it will kill all 8 of the dummies. No, don't move any further, simply press start, select restart last checkpoint!! Just do it until you get the achievement.