Verily! Allah forgives not setting up partners with Him, but He forgives whom He wills sins other than that, and whoever sets up partners in worship with Allah, has indeed strayed far away. 3.116
Shirk = unforgivable if one dies doing it.
All other things, Perhaps Allah (Swt) out of his Mercy will forgive us.
2nd thing) Following the Prophet (Saw) in all matters.
Say (O Muhammad صلى الله عليه وسلم to mankind): "If you (really) love Allah then follow me, Allah will love you and forgive you your sins. And Allah is Oft-Forgiving, Most Merciful." 3.31
It was narrated on the authority of Abu Najih al-Irbad bin Sariyah, radiyallahu 'anhu, who said: The Messenger of Allah, sallallahu 'alayhi wasallam, delivered an admonition that made our hearts fearful and our eyes tearful. We said, "O Messenger of Allah, it is as if this were a farewell sermon, so advise us." He said, "I enjoin you to have Taqwa of Allah and that you listen and obey, even if a slave is made a ruler over you. He among you who lives long enough will see many differences. So for you is to observe my Sunnah and the Sunnah of the rightly-principled and rightly-guided successors, holding on to them with your molar teeth. Beware of newly-introduced matters, for every innovation (bid'ah) is an error." [Abu Dawud & Al-Tirmidhi, who says it is an authentic hadith]
May Allah (Swt) send His Peace and Blessings upon the Seal of the Prophets and the Beloved (Saw). Ameen