At the end of the Granolah the Survivor arc, it was revealed that Frieza had become the new strongest warrior in Universe 7 after stumbling on a Hyperbolic Time Chamber out in space and training ...

Nightmare to you ... Directly comparing Super Saiyan Goku's speech on Namek to Frieza to Son Goku's, the latter doesn't hype himself up as a hero, but simply as a warrior filled with rage ...