Claude Rains did not receive an Oscar nomination for portraying Dr. Jack Griffin also known as the titular character in The Invisible Man.
Claude Rains one of the greatest character actors of all time had a rather peculiar breakout role to be sure. The Invisible Man was only the second film Rains was in, only having a supporting role in a silent beforehand, and despite being in the starring role of the film we only witness his actual face at the very end of the film for a brief moment. For the rest of the film Rains is either fully covered by clothing, or well rather hard to see. Nevertheless the film did give Rains the start to quite his long lasting cinematic career, and the main reason for that must have been his voice. This is actually somewhat similair to John Hurt in The Elephant Man in that both actors are physically onscreen during their performance, but technically speaking their work is almost vocal work in nature. This is even more true for Rains than it was for Hurt, as the disability involving Rains character simply only makes it so he can never be seen. Technically speaking Rains's physical performance is pretty straight forward which makes since in that Griffin is not suffering from his ailment at least not in a normal way.
Rains's voice is perfection for this role though as his voice does exude a certain class and intelligence just naturally. We don't need to know Griffin is a brilliant man because Rains sounds like such a brilliant man anyways. Rains in his earliest scenes, when he is all covered up, is actually quite good in portraying a more introverted quality in his voice in these scenes. He suggests a certain desperation in these moments as Griffin actually is trying to save himself from his invisibility, and Rains very nicely gives us the tragic side of the character before the villain side of Griffin comes out. This happens when, instead of being left alone to try and find a cure, Griffin is hassled by all of the town people leaving no choice for Griffin to reveal himself which reveals that there isn't much of him. Rains quickly becomes the monster who laughs his way through as he terrorizes the people who dare get in his way. Rains's is extremely entertaining in these scenes as there is such a relish of his evil acts through Rains's voice, and really Rains let's you basically in on the fun of all the acts random annoyance that Griffin is committing.
Where James Whale's earlier foray into monsters, that being the Frankenstein Monster, there was a great deal of woe in the monster. The Invisible Man on the other hand becomes a bit more directly evil even if there is a slight tragedy stated in that his evil is suppose to be a side effect of the chemicals that turned him invisible. For most of the film except for the beginning, and brief moments where Griffin interacts with his former love interest, The Invisible Man is evil and loves being so. There is extra degree of enjoyment of it as Rains's performance rather slyly makes a lot of what the Invisible Man is doing is the rather crude and cruel ego stroking of a once cultured and brilliant man. My favorite moments of Rains's performance are easily when he is terrorizing a former colleague of his who foolishly decides to call the cops on the invisible man. My favorite moment of these scenes is when Griffin discusses his plans which naturally include a few murders just for good measure. Rains is hilarious in the way he so matter factually states these things, and portrays the insanity Griffin in such an enjoyably proper sort of fashion.
Rains's performance here oddly enough is most comedic and Rains is actually quite funny in his portrayal of The Invisible Man's personal enjoyment of his random acts of evil. Rains though, even while being funny, does always carry himself with the right sort of menace at the same time, and manages to really make the fun of Griffin's behavior really a great deal of the basis of his evil. It's kind of a weird way for a performance as a monster to be, but everything that Rains does here does work for the film. This might not ever be the same type of challenge as some of his later, more physical, roles later in his long career, but it is its own challenge all the same. The fact that he is only a voice for most of the film never feels like a problem for Rains as a realizes Griffin as a compelling character all the same, and you have to think there is not even an animation of the character or something to help him the rest of the way. It's on Rains voice, and with his great voice Rains completely delivers in giving quite a marvelous performance of a marvelous character.