My power increases a little bit every second, and I become the most powerful demon

[Infinite growth + decisive killing + not suppressing the protagonist's level + system + demon cultivation + invincibility + empress's sister]
Lin Qingyun accidentally traveled through the fantasy world and became a tiger cub in the Ten Thousand Mountains. The tiger sister is the reincarnation of the empress and always wants to be his sister.
Fortunately, he got the infinite growth system at the beginning, and his demon power increased a little every second.
Three years of demon lord, ten years of demon saint, from an ordinary golden tiger, his bloodline continued to evolve and became the most terrifying demon in the entire continent.