Technically any market that's about someone doing something by a certain time can be an assassination contract, if you think the market will it enforce it that way. Can't do it if they're dead.

It was kind of close to that betting on Trump to not win the last election - $3.2bn was bet on Trump vs Kamala and there was of course an assassination attempt although not related to the betting.

“Markets related to death are technically not supposed to be allowed at regulated prediction markets in the US.”

https://nexteventhorizon.substack.com/p/the-chaos-of-khamene...