Lord Boros is a monstrous fighter who travels the universe looking for worthy adversaries. He serves as the central antagonist of One-Punch Man Season 1 and ultimately meets his end against Saitama. Many fans of Dragon Ball notice a striking resemblance between Boros and Son Goku himself. One Punch Man serves as both a loving tribute to and parody of typical shonen manga. Does Boros simply reflect your typical shonen character, or is he more specifically a spoof of Goku?
Boros bears some physical resemblance to Goku. His build is similar to Goku, though heavily defined musculature is by no means unique to the hero of Dragon Ball. The more striking similarity fans point out is the hair. While many anime protagonists have spiky hair, there is no missing the fact that as Lord Boros changed form to increase his strength, his hair grows in a way that echoes Super-Saiyans. The fact that Boros undergoes multiple transformations that unleash consistently greater power is in itself completely reminiscent of Dragon Ball. However, one could argue that since the physical transformations are so distinct Boros more closely resembles Frieza than Goku.
If there is a classic central motivation for characters in shonen manga, it's "Stronger, Stronger, STRONGER!!" One-Punch Man is a subversion of this trope. In manga such as Dragon Ball and Naruto, the power levels of the main characters need to become more or less ridiculous just to keep the momentum going. After all, if Goku simply maxed out his power levels, in many ways there wouldn't be anywhere left for the story to go.
It would be one thing if increasing power was a plot device, but it's actually Goku's primary motivation as a character. All Goku really wants out of life is to become stronger and more skilled as a fighter. He cares about his family and friends, but in truth, he is pretty self-involved and somewhat amoral. He wants to fight the strongest opponents possible to test himself. Whether he's fighting Frieza, Cell, or Majin Buu, improving his own abilities is his central goal, as opposed to protecting the innocent population of earth.
Boros shares this trait. He represents what Goku could be if he did finally max out his power levels. Boros has become the strongest entity in the universe, but still wants nothing more than to fight worthy opponents. Whereas Goku stays home and more or less lets incidents come to him, Boros has to be more proactive, seeking out fighters throughout the cosmos. It is a boring, unfulfilling existence-- and more or less a parody of what would happen to Goku if he achieved his greatest wish.
It seems likely that Boros is at the very least a riff on Goku, if not an outright parody of him. With the transformations, the hair, and the motivation, he absolutely screams Dragon Ball Z. Ironically, though, One-Punch Man doesn't punch it's targets of parody too hard. Boros is depicted as more or less evil, but let's not forget there's another character in One-Punch Man obsessed with strength and more or less indifferent to the general populace.
That's right, it's Caped Baldy himself, Saitama! While it's easy to point at Boros as the character more closely inspired by Goku, Saitama walks in his spiky-haired shadow as well. The inspiration at this point runs in two directions! Akira Toriyama seems to have turned the tables on One-Punch Man, as the character of Jiren from Dragon Ball Super seems to be inspired by Saitama, with a similar move set and existential crisis.
We might never get a confirmation on whether or not Boros is a direct spoof of Goku, but it seems fairly clear that inspiration runs deep. As long as Dragon Ball and One-Punch Man continue to feed off each other and generate great content, we can be sure of who the winner will be in their rivalry -- the fans!