Is the sin of wasting seed as severe during the night when you are not in control of yourself as severe as when you do it intentionally?
Intentionally is much, much worse, but that doesn’t mean that unintentionally is permitted or that it isn’t a serious sin. There are numerous halachos that are based just on the fact that if a person sees immodest things, or has too much contact with women, that it will bring him to have erotic thoughts at night, which will cause him to involuntarily be motzei zera. So both are terrible. Let’s compare it to man slaughter or murder, see NIdda 13a.