User blog comment:MarvOfficial/Hey.../@comment-27812664-20180417011259/@comment-27812664-20180417185702

Let's see...

Metal Sonic (introduced in Sonic CD)

Metal Sonic 3.0 (Sonic Rivals 2)

Silver Sonic (Sonic 2 Game Gear/Sonic Mania)

Mecha Sonic (Sonic 2 Genesis)

Mecha Sonic (Sonic & Knuckles)

and finally...

Unnamed Sonic Robot (Sonic Adventure)