Thanos became a universe with a cube once.
During the Chaos Engine trilogy, a single, nascent cube was able to stack 3 seperate universes on top of the 616 reality nearly causing the multiverse to collapse.
The Badoon enslaved hundreds of Celestials using a single cube. According to Kubik, this shouldn't have been possible.
In Paradise X (non-canon) the super heroes and villains of that reality all ingested small fragments of a cube and became Gods; going off to create their own universes.
Those are the most notable ones off the top of my head.