Ultra Instinct Sicko Mode is the highest level of sicko mode that can currently be achieved. It is where a person ascends to the highest level of existence. This results in the sudden absolute peak of physical and intellectual prowess where a person can act purely on instinct. As such, this mode is another way of saying that they are immortal.
"Holy fucking shit!! Daniel... he's going Ultra Instinct Sicko Mode! There's no way we can possibly defeat him now!!"