I was thinking about this in relation to Beerus and thinking back from there. It would seem Goku has changed many characters, especially villains, that he has come into contact with. The ones that were not changed at all ended up dead in most cases (if I am remembering correctly). So what impacts can you remember Goku having on characters throughout the entire series?
Two big ones come to mind and that is Piccolo and Vegeta. His interactions with them both ultimately changed them on various levels. Piccolo became more understanding and compassionate and Vegeta ended up caring deeply about others, more so than his own life. Being that Piccolo started out as King Piccolo, a demonic hellspawn of a Namek and Vegeta was not only a Saiyan but a prince, I'd say that is quite impressive changes for both of them.
Two big ones come to mind and that is Piccolo and Vegeta. His interactions with them both ultimately changed them on various levels. Piccolo became more understanding and compassionate and Vegeta ended up caring deeply about others, more so than his own life. Being that Piccolo started out as King Piccolo, a demonic hellspawn of a Namek and Vegeta was not only a Saiyan but a prince, I'd say that is quite impressive changes for both of them.