Andy Robinson did not receive an Oscar nomination for portraying the Scorpio killer in Dirty Harry.
For the first third of the film or so we mostly see the actions of Scorpio as he murders people and leaves ransom notes demanding money to be paid or else he will commit more murders. The first murder we barely see him but the second attempted murder we see Scorpio make his preparations. Robinson is exceptional in the scene as we see Scorpio mark his target. Robinson is quite chilling in the scene as he loses his mark then he finds his potential victim again. Robinson is great as he brings the most eerie smile over his face as Scorpio sees his chance to murder has returned, in his expression he shows the sick sadism of Scorpio very effectively. We don't learn why he does this, but from here we can see he certainly enjoys it.
Once we see more of Scorpio Robinson makes a most unusual but remarkable dynamic for his character. Robinson makes Scorpio a very pathetic and very threatening character all at the same time. Through his meek posture and his squeal Robinson makes Scorpio clearly a weak and very lowly individual. In this though Robinson brings an unpredictability of the man through the viciousness of his psychotic behavior. He mixes in the violence with his overall lowly state to make this a very visceral performance. Due to his more pathetic qualities when Robinson brings out the violence it is all the more jarring and Robinson makes every scene with Scorpio have an underlying intensity as you don't know what he is going to do.
Scorpio is a most interesting adversary for Dirty Harry as the only quality they share is their ability they share is their ability to kill fairly efficiently. Where Eastwood stands tall, Robinson well stands short, Eastwood's voice is firm and forceful, Robinson is fluttery and whiny, where Eastwood makes Harry emotions rather self contained that although can be intense are always in control, Robinson shows Scorpio become an emotional mess very easily. This juxtaposition absolutely works as Eastwood and Robinson complement each other's performance marvelously. Their scenes together have a raw power as both go all their way in their differing characters making for some very memorable moments particularly the torture scenes with Eastwood being so controlled and Robinson being such a wreck.
Robinson's turn as Scorpio is a bit underrated as villain turn goes and his influence is rarely mentioned as I think you can see some of Scorpio in Heath Ledger's performance as the Joker. The crazed psychopath is easily a part that an actor can go too far with, but Robinson handles it incredibly well by showing the way the extreme craziness comes out at certain times. Robinson builds to it as it becomes time for violence that is when Scorpio begins to well lose his composure a bit. Robinson handles the progression in natural fashion even though this is not a case of the evil coming out, and even when Scorpio seems come Robinson plays him in a particularly slimy way. This might not seem like a large leap but Robinson makes an art of going from slime to psycho.
Robinson makes Scorpio a most despicable and completely unsympathetic villain, and that is completely the right approach. He never takes a step back showing Scorpio revel in everyone of heinous acts, Harry says Scorpio likes to kill and Robinson supports this point. This is the best approach in the film as we want Harry to torture Scorpio, and we want him to kill him at the end with that build up to the 6 shots or only 5 scene at the end of the film. Robinson is great in making Scorpio the lowest of the low. He is creepy, one scene where he walks through a park is especially off putting as he looks so happy around children, he is threatening, he is just all together deplorable. Robinson makes a great villain you hate, and takes an interesting approach that absolutely works where he is not the equal to Harry but rather a brilliant subversion.