Orin Scrivello is a cruel, sadistic and treacherous dentist who shows some symptoms of being a sociopath due to his relishing of other people's misery. Although definitely a villain, he didn't survive very long as his own maliciousness proved to be his undoing as Seymour plots to murder him and feed him to the main antagonist, the monstrous plant known as Audrey II. During his song, he admits to shooting puppies with a BB Gun, poisoning guppies and finding cats and bashing their heads as a kid.
In his deleted song ("I found a hobby"), it delves further into his love for torture. He mentions that when he was ten years old he saw his first horror feature, to which he got an erection.
Orin Scrivello is portrayed from the start as a troubled man who is likely insane yet has managed to be a successful dentist (it is implied he is a success due to his talent to inflict torture on others, a stereotype of dentists). He takes delight in his job, where he is free to abuse staff and customer alike without care. However, he comes into conflict with Seymour when he begins to date his love interest Audrey. Upon witnessing Orin verbally and physically abusing Audrey while Audrey II is goading him to feed her someone who deserves to die, Seymour plots to kill his rival and feed him to the plant in revenge.
In order to do this, Seymour heads over to Orin's surgery to take him up on a previous offer of a free root canal. Unfortunately, he arrives at Orin's surgery just as he had finished trying to torture a masochistic patient. Enraged that he couldn't install fear or pain into the demented patient, he set upon Seymour with sadistic madness, forcing him into a room where he began to torture him. Wanting things to be "special", Orin puts on a bizarre mask that allowed him to breath in laughing gas, making him high.
Orin became disoriented as a result and although clumsily trying to continue the torture ended up falling over, Seymour pulled out a gun and threatened to shoot Orin but couldn't bring himself into committing the deed. Regardless, Orin was already doomed as his mask malfunctioned and he fell to the ground, beginning to choke to death. Orin's last words were "What did I ever do to you?" to Seymour, who responded "Not what you did to me, what you did to her" and Orin looked puzzled before he finally realized and died with the final line: "Oh.. her.." - his body is later fed to Audrey II by Seymour.
Audrey later expresses guilt over Orin's death despite not being involved because she had always secretly wanted him to disappear due to his behavior towards others. She was likely far from the only one who wished such a fate upon him.
Little Shop of Horrors - Dentist Song
He is commonly mistaken as the main antagonist of the movie. However, Audrey II is the main antagonist since Orin only makes a few appearances throughout the movie, plus Twoey had bigger plans than anyone else.
Audrey mentioned that she only dated Orin because he gets paid a lot as a dentist and she barely makes any as a florist at Mushnik's failing shop.
This is parallel to why Seymour put up with the movie's real main villain, the plant (Audrey II).
His last words differ from stage to film. In the stage adaptation, his final words are "Are you dumb or hard of hearing? Because for me the end is nearing. Are you satisfied? I laughed myself to death!" (often with Seymour finishing with "death") but in the film his last words are "What did I ever do to you?" and then Seymour says "Its not what you did to me its what you did to her," causing Scrivello to say "Her - who? Oh, her," and then dying. The film changed a lot of the stage adaptation dialogue and even changed the finale, but this was most likely done for screentime and to appease audiences.
His appearance and vocal chords are reminiscent of Elvis Presley.