Rumple in Once Upon a Time is one of the most frustrating characters I've ever encountered.
Yes, he's mostly a villain, but the lengths he goes to are insane. He's killed hundreds, if not thousands. He's ruined the lives of hundreds. He's actively backstabbing his own friends and family constantly. He's a manipulative coward who cons his way into a dishonest, toxic marriage. He's always out for himself...
... Which is why it's frustrating that the main heroes KEEP GIVING HIM ANOTHER CHANCE, despite hundreds of years of history, both old and VERY recent, saying he really doesn't deserve it. The show paints him as an antagonist, but when it tries to make us sympathize with him time and again - his bad father, his strained marriage, his lost child, etc. - it never once feels like it succeeds at making the audience root for him - either to succeed or be redeemed.
I haven't finished the series, but I think I'm in the final season and he's still just as awful as he's always been, despite sad or sentimental music playing whenever he talks up wanting to reform.
Honestly, I wish they'd just let me love to hate him, because it never makes me hate to love him.