1.I wonder whether the word "avenge" implicits they avengers are doing something for justice while the word "revenge" refers to something negative.
2.As I know, "avenge" is a transitive word. But I am not sure whether the sentences below all make sense.
(a) He avenged his father on the murderer.
(b) He avenged his father's death.
(c) He avenged the murderer who killed his father.
Thanks a lot.