If you are talking about slot games from third-party providers, then, personally, I haven’t seen any and I doubt you will ever see one that has a 100% RTP. The reason is that there is no financial incentive for the casino to add one. 100% RTP means 0% house edge which in return means the casino will make no profit from it.

However, you can find 100% RTP o 0% house edge games and they will most likely be original games. Just like the one mentioned by Pmalek.