"There was Antonin Dolohov. ... I-I saw him torture countless Muggles and - and non-supporters of the Dark Lord."
-- Igor Karkaroff giving testimony in Dumbledore's Pensieve memory (GF30)
Antonin Dolohov was a particularly sadistic Death Eater, one of Tom Riddle’s friends after leaving school (HBP20). He was sent to Azkaban for the murders of Gideon and Fabian Prewett (OP25).
Dolohov escaped from Azkaban early in 1996, along with Bellatrix Lestrange and several other high-security prisoners, and rejoined Voldemort. He participated in the Battle of the Department of Mysteries and was recaptured. Dolohov’s “specialty attack” was a jet of purple light cast in a zigzag pattern which causes severe internal injury (OP31). He used this on Hermione. Dolohov was also the one to use “Tarantallegra” (Dancing Feet Spell) on Neville, which caused the prophecy to break when Neville’s dancing leg kicked it (OP35).
Released again from Azkaban, Dolohov attacked Harry, Ron, and Hermione in a café on Tottenham Court Road with Rowle (DH9). During the Battle of Hogwarts, Dolohov killed Remus Lupin (DH31, BLC, Pm). Later, Dolohov was on the lookout for Harry with Yaxley in the Forbidden Forest, eventually having to report to Voldemort that Harry hadn’t come (DH34). When fighting began again, Dolohov was finally taken down by Flitwick (DH36).
Dolohov's "specialty attack" was a jet of purple light cast in a zigzag pattern which causes severe internal injury (OP31). He enjoyed torturing "countless Muggles" and "non-supporters of the Dark Lord" (GF30).
Appears to be named for the character Dolokhov in the Russian novel War and Peace by Tolstoy:
Rowling had seen [actor Tom] Burke’s brooding Dolokhov in "War And Peace" and was already a fan. She took special note of him because Dolokhov is her favourite character in Tolstoy’s novel – she even named a character in Harry Potter ‘Dolohov’ in homage. ‘She approved of my interpretation of Dolokhov,’ laughs Burke, ‘and she seemed happy with my casting. She’s seen the first episode of The Cuckoo’s Calling now and has said she’s very happy. (Benji Wilson. "Event Goes On Set of JK Rowling's Wizard New TV Thriller." Daily Mail online, 12 August 2017).
Because the books only states that Harry "saw Dolohov fall with a scream at Flitwick’s hands," it's not 100% certain he was actually killed (DH36).