If you are looking for a voice that will always draw attention for a variety of reasons, include a character with a stutter voice. Whether it is the hero trying to overcome a personal inhibition or a villain striking back for a lifetime of being made fun of, the stutter grabs centre stage and makes the audience lean in.
No voice evokes pity or compassion quite like the stutter voice. It slows down speech and makes you pay a lot more attention to make out what is being spoken. A lack of confidence or extreme anxiety is often given as the cause of the malady and the stutter is often something for the hero to overcome as in the King's Speech with Colin Firth. Or else it might be used to heighten a villain's rage at how they were mocked and bullied as a child which sent them on their path.
It is not an easy voice to listen to but it does draw attention and usually a sense of empathy and compassion from the audience. Even if the stutter voice is that of the villain it can give the audience a sense of pity in terms of at least uunderstanding a huge part of why the antagonist ended up this way.
Stutter voice is characterized by repeated letters or sounds as a disruption to the normal pattern of speech. A person may repeat the same consonent such as "K" "G" or "T". They may have difficulty uttering certain sounds or starting a sentence.