Asura-He is an immortal being that that self-doubt would create a Heartless form but he would destroy it when creating himself as a Nobody. Making himself more powerful to destroy his enemies, and quite possible to become another Xehanort.

Esdeath-Like Asura, Esdeath is devoid of good emotions. So her anger and lust would create a Heartless form that would embody her darkest emotions while her Nobody form would contain her emotions for Tatsumi while increasing her Ice Imperial Arms abilities.

Father-Father desires to become the perfect being so he separated his seven sins which each become a Heartless, so after doing that he would become a Nobody but with intense power.

Izaya Orihara-He is a person who loves humans, but his desire and negative emotions would turn him into a Heartless. But a member of the Organization would turn him into a Nobody so he can also become quite possibly the newest Xehanort.