NOTE: There have been many incarnations of King Ghidorah over the years, but per rules we are using the most recent Keizer or "Kaiser" Ghidorah who was Godzilla's final opponent in Final Wars.
Keizer Ghidorah can fire gravity bolts out of each of his three heads, and can also unleash a high telekenetic blast (much like that of Space Godzilla's) that allowed him to lift and throw Godzilla. His bolts, when fired from all three heads, are more powerful than Godzilla's only radioactive blast. Oddly enough, despite having wings, it seems unlikely, due to weight and shape, that Keizer Ghidorah can use them to fly. His flight abilities allow him to use his own massive bulk as a deadly weapon. He possess greater physical strength then then he did as Monster X. His last ability is to bite onto his enemies and drain out their lifeforce. Because of his great strength and the fact that he drains the very life of his foes, breaking the grip is nearly impossible. In all, Keizer Ghidorah was already an extremely deadly monster as Monster X, but as Keizer Ghidorah he's even more powerful.
http://godzilla.wikia.com/wiki/Keizer_GhidorahA longstanding figure in Japan pop culture, Ultraman is one of the earliest humanoid sci-fi combatants.
Ultraman is an very accomplished hand-to-hand fighter, able to pull of attack moves and combos with phenomenal skill, speed and accuracy. He can vary between human size and 40 meters tall depending on opponent size. He also has varying telekenetic abilities, and a space armor that can protect against most attacks.
In addition, Ultraman has an assortment of energy based attacks, most notably the Spacium Ray that can finish most opponents. He also has a ring that can fire the Ultra Slash.
Ultraman's main weakness is that he can only remain powered on Earth for 3-5 minutes before requiring recharging in the sun, or returning to his human host. However, since Slugfest battles are on a celestial plane away from Earth, this may not be a problem.