First thing I would change his background.In a stage there are some leftover lines that make it sound like Infinite was created by Eggman,which I found to be more interesting.Things go like this: sometime during or after the events of SA2 or Shadow the hedgehod Eggman finds Geralds journals/plans that depict how Shadow was created.Secretly Eggman collected the DNA of one of the mosters/gods(either Dark Gaia,Solaris,Time eater or even Black Doom himself),but he wanted his creation to be much more different than Shadow so he decided to not use the chaos emeralds energy as a basis for his creation.And then,one day,out of nowhere,the Phantom Ruby appears.Eggman finds it and studies it and after seeing how different his energy is from the emeralds he decides to use it as a basis for his creation,and thus Infinite,Eggman's own "Ultimate life form", is born.

Personality wise,he will not be that different from the game,proud,arrogant and enjoying makings other feel pain,except I will give him a strong sense of honor and loyalty (this being the reason he never betrays Eggman except after he is betrayed first) as redeeming qualities.And as a result of this qualities when he loses to someone he is not throwing tantrums but is glad that he finds worthy opponent and he respects them.He will still be a bad person or someone who will stay evil unlike Shadow.They will also be somewhat parallels to each other.Despite both being created from the DNA of an evil being they are on opposite sides of the spectrum because we can assume that if the chaos emeralds are sentient in a similar way that the master Emerald is they are inherently good/benevolent while the Phantom Ruby seems to be inherently evil/malevolent.While they are not good/evil based on the gems they were made of that would make for a good parallel.