Ramlethal Valentine is a character in the Guilty Gear series, who first appeared as a non-playable boss character in the arcade version of Guilty Gear Xrd -SIGN-. She later became a playable character in an update on April 8, 2014.
A lone girl who declared war on the entire world, she is a non-human life form born in the Backyard, which governs all of creation. Her relation to the Valentine
who orchestrated the prior Baptism 13 Incident (the Illyrian Invasion)
is unknown. As an assassin of the Merciless Apocalypse, her objective is
the extermination of the human race, and to that end she has formed an
alliance of convenience with the United Nations Senate. Waking of the
“Cradle” is her sole objective and mission.
I'll leave it at that because her story's incredible and I don't wanna spoil it, so if you're a Guilty Gear fan, I highly recommend running the Story Mode in Xrd -SIGN-.