How to disable defualt roblox animation?

If you just wanted to stop any sort of animations running in your character, the only thing you'd need to do is put an empty/disabled LocalScript named "Animate" in StarterCharacterScripts.

Though, if you wanted to replace the animations instead, you'd have to:

1. Get a copy of the Animate script for the RigType (R6 or R15) you're using in your game.
2. Edit the contents of the script, particularly the table with the assetIDs, replacing them with the assetIDs of your own animations.
3. Place that localscript inside StarterCharacterScripts, and you're done.

If you're letting the players pick what rig they're using, then I suggest creating a Server script to handle which Animate script you're going to insert in the player characters, while having an empty Animate script inside StarterCharacterScripts.

Hope that helps!