Anti-cheat system:
I propose adding a hitbox to each player that limits their movement speed.
What do I mean?
Each player has an invisible hitbox, either square or spherical (your choice). It moves with the player with a delay of 0.5-1 second and contains a script that teleports the player to the center of this hitbox if they suddenly move outside of it.
This hitbox is larger for speed abilities, such as Devourer of Souls (15-300 kills), etc.
It also disappears if the player is in a ragdoll.
If a player is teleported back more than three times within a few seconds, he is kicked out of the game.
||If anyone has any ideas on how to make this better, the comments are open to you.||