So I'm writing a story and my main antagonist is Death (At least from my MCs point of view). Is he as a antagonist too cliche? He owns a casino, his headquarters, and the setting is in 1700, London during a plague.
Your character sounds a little like Randall Flagg from The Stand: Flagg makes Las Vegas his headquarters, and a plague is present. From the information given, I would imagine you have read the Stand.
Now, that doesn't make it cliché, as one can still only claim a similarity between the two characters (not a cliché). However, seeing how people are still reading the book, going on half a century after it's publication (it's still in almost every bookstore I've been to), how a TV-series was made of it 30 years ago, and how they made another TV-series out of it last year or so, you might risk people seeing as a cliché, even if it isn't one.