Marvel: Mutant Absorption

Onslaught
As a psychic entity, Onslaught had the ability to absorb any mutant into his being and thus permanently gain their powers for himself. X-Man and Franklin Richards were two mutants that he consumed to increase his vast power. In the hypothesis of Onslaught's connection being disrupted or destroyed, it would halt his process of evolution, as happened when Xavier was still inside him. Someone absorbed is completely dominated without consent when their willpower is inferior to the control exerted.