Guardian Ghidorah is pretty unique. A tooth and claw Ghidorah and he walks alongside the forces of good. Also being supernatural as oppose to an extraterrestrial.
Ghost Godzilla out of all the Godzillas just seems the most unique as he is the resurrected God of Destruction. Can absorb spiritual energy. Showa Godzilla and Shin Godzilla would also be good picks if this Godzilla didn't get in.
The Armored Titan in the last of the Toho Titans to not be featured. He is way just as skilled as the Rogue Titan in combat and has a armored hide to protect him from attacks (As his name implies.)
Mothra (Legendary)