Amalek and Dormad* were aliens that could compose themselves in energy state of being (although its not known if the latter ever gained the ability to reinstate into a corporeal form) and journey to Earth to threaten Superman with their presence.
In Amalek's case, he was a pirate defeated by Earth-One's Last Son of Krypton, causing the villain to seek revenge on all members of the hero's race. In Dormad's case, he and his crew merely crash landed on Earth-Two which would've caused destruction were it no for his ability to communicate with Superman's niece Susie, her uncle sending them home.
Dormad's ship returned to stage a fake invasion, an elaborate scheme with the intent of revealed of Superman imposter. Amalek himself schemed to frame Superman for the pirate's murder, even threatening the life of his mortal enemy's cousin Supergirl. This confrontation, however, ended up failing while still causing the rogue his own life.
*Dormad is not the real name, but a unit of measure from that alien's perspective. However, as this is the sole term used from the alien's language during the story, we use this as an identifier.