Iczer is a cult classic dark anime series from the 1980's. Based on a manga, there are 3 OVA's - Fight! Iczer One, Iczer Girl Iczelion and Iczer Reborn (or Adventure! Iczer 3). It starts with an invasion of Earth by a race called Cthulhu (yes Cthulhu).
Iczer is a very strong verse, with multi-solar system busting characters, massively faster than light travel, time resets, and more.