The first time i tested minecraft 1.17 i generated a wither and the wither give me a lo of lag, the game becomes unplayable because the wither destroy anything he see, please mojang fix those bugs because the wither always give a lot of lag i mobile devices, a lot of people i imagine that when they go tod defeat the wither boss, doesnt care the phone but the game lags a lot with the withers, until top gamma phones lag a lot for the guilt of the wither, i can say the wither lags more the world than tnts