Real life villains can be likable. Ted Bundy was known for being so charming and charismatic that even the judge at his trial was reluctant to punish him. His childhood had been horrific and it’s highly likely he was the product of incest. Life had done him immense harm he didn’t deserve.
That didn’t change the fact that he’d raped and murdered more than thirty women and girls. A tragic back story couldn’t save him from execution, nor would it bring back the lives he’d taken before he went.
Your villain can be likable, pitiable, kind, or even promote a moral cause (see Erik Kilmonger in Black Panther). However, those traits must not outweigh the bad they’ve done that they do not regret.
If you don’t want them to outshine your protagonist, you must make both individuals worthy of being in conflict with each other. Your protag might understand and weigh the circumstances of the villain’s evil, but ultimately make the right decision in opposing them.
