Someone explain to me how that slime got that hells strong

stronk slime

If a monster attacks a player and win, it will get exp. If two monsters attack a player and win, those two will get exp (out of 10 the two of them get 5 or 10, I don't remember if it's divided or everyone gets the max amount). So if the slime punched once a player who die later in that fight, the slime gets the exp too

Sorry if it's not understandable, not my first language ヾ(❀╹◡╹)ﾉ~