Drop them.

No, seriously. Roleplaying involved running a faulty character, one with strengths and weaknesses. This is especially true in freeform RPs, which don't have a hardcoded set of rules to allow a clear victory/defeat condition with an action. Other PCs won't want to interact with the always-victory character, because they always lose when facing them and their problems are instantly resolved when working with them.

If you're keeping the player in the RP, then be aware that most people are likely to just ignore the player, or get annoyed when they're involved in anything beyond casual interaction. As mentioned above, they either win all fights against PCs (which could be drawn-out and bog down the RP) or they win all fights against the PCs enemies (which sidelines the other PCs). Either way, after a bit nobody will want to interact with the character.

You'd probably want to make the player aware of that, and note that you will be forced to kick them if they become a bother to other players. Other than that, just recommend that the character has some real flaws, and that the player actually makes use of them.


As an aside, I would not follow the "Let the character always win" idea. This just sounds like turning them into a Mary Sue to me, which is going to be just as boring.