https://www.mangago.me/read-manga/i_have_to_be_a_great_villain/ (an obvious answer but worth a try)
And there's this non BL manhwa. Both ML and FL fell for the second lead (the MC). it's neither bl or nor romance bc it just tackles abt the changes of the story
Not exactly as a villain but the ML takes interest in him instead so If you're okay with that here ya go (◡ ω ◡)
https://www.mangago.me/read-manga/stuck_in_my_sister_s_dating_sim/
A bl where the protagonist enters a game/novel as villian but the ML takes interest in him instead of FL. ╥﹏╥