Kimera

Both are 90s OVAs about vampires with an... extra terrestrial twist, and a special vampire that holds the key to saving the world, or destroying it. 

Both have Vampires, Sci-fi, sad love story. Vampire Hunter is far more powerful though. 

-Both ova start out with Earth being struck by a pod /meteorite containing alien lifeforms; -Both involve a mysterious green haired beauty that turns out to be crucial element in determining humanity's fate; -In both of them the girl is found in the streets by some random guys because who just doesn't pick up from streets a seemingly inofensive naked chick; -Both ova are sure to provide you a good laugh, more or less intentionally because of how poorly done they are and how surrealistically hilarious they can get. The difference is that Injuu Daikessen seems like a train wreck intentionally, while Kimera is more of a bad adaption that takes itself a bit seriously. read more 

Both anime deal with main protagonist having romantic feelings for a powerful creature. Both Kimera and Pupa are very grotesque and contains violence, blood and gore. However Kimera has no incest. If you like one, you will enjoy the other. 

Both OVAs are filled with violence, blood and nudity. They also have non-hentai grotesque tentacled monsters. If you like one, you will enjoy the other.  

Mythical deadly beings, the ones loving/protecting them against all common sense, and how one's personal decisions impact the world's future. Both involve a beautiful, golden-eyed gender fluid main character (sexless in RG Veda, hermaphrodite in Kimera) which turned female in the english dub/sub, nevermind the story being played out in BL flavor. Despite their flaws and limited budgets, they're a short and decently compelling watch if you can't lay your hands on the manga or simply enjoy dark, exotic fantasy OVAs with vintage vibes and aesthetics.