Answer: - Complete salvation is that after attaining which one never takes birth again. The cycle of birth and death ends forever.
Bhagavad Gita Chapter 15 Verse 4
It is mentioned in Gita Chapter 15 Verse 4 that after finding the Tatvadarshi Saint, slashing the ignorance with the weapon of tatvagyan, that is, properly understanding the knowledge, after that one should search for that supreme state (Satyalok) of Supreme God; having gone where, worshippers never return to this world, that is, they are never reborn.
This is complete salvation which ends the cycle of birth and death.
The God who has done the entire creation, only worship Him to attain complete salvation.