These days aimbots are so sophisticated and able to include fuzzing, that it's virtually impossible to tell because they can mimic a player's movement, miss occasionally, etc.

About the only cheat you can really identify is glass-walling, because usually people who do it eventually slip up and aim/shoot perfectly at someone they plainly cannot see.

Really good players can get lucky pretty often because of game sense so even glass walling is hard to detect for certain if a player shoots through walls and kills their invisible opponent. We see this often even in pro play for tactical shooters.