Eternal sin
Thomas Aquinas lists, or has responded to, six sins that supposedly go against the Holy Spirit:
Thomas Aquinas explains that the unforgivability of blasphemy against the Holy Spirit means that it removes the entrance to these means of salvation; however, it cannot hinder God in taking away this obstacle by way of a miracle.
Tikkun HaKlali
Although the sin of wasted seed is considered the most serious of the violations of the Covenant, other sins also accomplish the same thing. Rebbe Nachman taught that one who earns his livelihood dishonestly also breaches the Covenant, as his craving for money can make him go so far as to rob his fellow man. The way one thinks, speaks and acts are also areas in which he can uphold or damage the Covenant.