Jemm

Jemm was a powerful alien convict.

Riot at the D.E.O
Jemm was arrested by the D.E.O and attempted to use his telepathy powers to escape his cell, though he failed due to the cell's special wall. Later, an earthquake occurred and the D.E.O Headquarters locked up all the exits and went to emergency status. Jemm used the mess to try to escape. Hank Henshaw (J’onn J’onzz), Reynolds and Tsung then began hunting Jemm in the base. Jemm then ambushed the group, killing both Reynolds and Tsung.

Death
He later ambushed Alex Danvers and Donovan while they were on their way to Henshaw, he entered Donovan's mind, Donovan told Alex to run. Jemm then took full control over Donovan and killed him. Alex then confronted him, shooting him with several different weapons to no avail, only damaging Jemm's head. When Jemm was about to kill Alex, Henshaw arrived and strangled Jemm to death.