Dr. Doom- Secret Wars

In the Secret Wars crossover comics Dr. Doom is faced with a strong enemy, The Beyonders. The Beyonders are a race of omnipotent aliens who are hellbent on destroying the multiverse. In order to stop The Beyonders from getting what they want, Dr. Doom destroys the multiverse himself.

Doom is able to save bits and pieces of different, parallel, worlds where The Beyonders were going to completely destroy everything. 

Molecule Man gives Dr. Doom his power. He tells Doom to find all of the alternate versions of himself, throughout the parallel worlds, and murder them to absorb their power as well. Doom takes a new identity, Rabum Alal, and kills every version of Molecule Man to become more powerful. In an epic battle Doom defeats The Beyonders and absorbs their power. He combines the bits and pieces of different worlds into one entity called Battleworld.

Dr. Strange helps Dr. Doom along the way and, together, they erase the memories of anyone inhabiting Battleworld so that no one remembers what life before.  

Dr. Doom crowns himself the God Emperor.