What is the ruling on a non-Muslim entering Paradise if they dedicated their life to serving humanity, and does the verse "Indeed, he who associates others with Allah - then Allah has forbidden him Paradise" mean that a polytheist is someone who fights Islam?

Defining a polytheist as an enemy of Islam is an evasion of the conclusive text that forbids Paradise to the polytheist. The verses revolve around the oneness of God and His exclusive right to be worshipped. Polytheism nullifies good deeds and necessitates eternal Hellfire; it is the only sin that God does not forgive if its perpetrator dies upon it. Explicit sacred texts from the Quran and Sunnah (definition) have indicated that only a Muslim soul enters Paradise, and whoever dies upon disbelief shall never enter Paradise. As for the good deeds performed by polytheists and disbelievers in this world, Allah the Almighty rewards them for them in this world, and they shall have nothing in the Hereafter except the Fire.