User blog comment:Echo 1/Elements You Should Not Give Your Characters/@comment-5918010-20130511184258

Other elements not to use:

Supernova- destroys everything in sight and more.

Black Holes- same thing (unless they are micro black holes)

Space- potential to end the universe (maybe ok if it is under control)

Energized Protodermis- could destroy your enemy, or make them more powerful (kinda a double-edged sword)