Emitting Seed in Vain

Hello and blessings

The sin of one who emits seed in vain is indeed extremely grave; see here. However, it is clear that repentance is effective for every sin and transgression, including this sin. Of course, the repentance must be serious, with wholehearted resolve not to sin in this way again, to distance oneself greatly from everything that leads to it, and to confess before the Creator of the world about the sin.

See here for more detail on the proper path of repentance for this sin

With blessings,

Binyamin Shmueli