Bender Gets Made (a.k.a. Bendfellas) - S2-E17
Other mistake: The strap for Leela's eye-patch on the right side of Leela's head (from her perspective) goes just over her ear. The left side goes above her ponytail. This would prevent the two ends of the strap from meeting.
Bender Gets Made (a.k.a. Bendfellas) - S2-E17
Other mistake: At the end, when Fry, Leela and Bender are sitting at the table, Fry's legs disappear (and the gray blotch beneath him isn't them - it's the table leg; and it's not hiding them either - his knees should be visible behind it). (00:21:35)
Answer: You are thinking about episode 20 of series 2 - "Anthology of Interest I". She technically never kills anyone, but in the episode she ask a "What if machine" (one of the Professor's inventions) what would happen if she was more impulsive. The machine then shows the more impulsive Leela killing off the Professor to get the money from his will and thereafter killing Hermes, Bender, Scruffy, Cubert, Nibler, Amy and Zoidberg to cover it up. Finally she does something really impulsive with Fry.
Andreas[DK]