ARMORED TROOPER VOTOMS: THE BIG BATTLE

Big Battle is a one-shot OVA set after the climax of the original Votoms storyline, but before the epilogue at the end of the series itself. With the Gilgamesh and Balarant forces still trying to advance their PS programs, Chirico and his old friends are forced into one last gladiatorial battle against a special PS and a formidable land battleship. — Description from AniList community (anilist.co).