what does this cutter refers to?
It is the fourth season premiere of the American television drama series "Breaking Bad".
Box Cutter (Breaking Bad)
"Box Cutter" is the fourth season premiere of the American television drama series "Breaking Bad", and its 34th episode overall. 
who did gus kill with a box cutter Gus slices his loyal henchman Victor's throat with a utility knife.
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Box Cutter (Breaking Bad) [SEP] Introduction
"Box Cutter" is the fourth season premiere of the American television drama series "Breaking Bad", and its 34th episode overall. Written by series creator Vince Gilligan and directed by Adam Bernstein, "Box Cutter" originally aired on AMC in the United States on July 17, 2011. The narrative follows protagonist Walter White (Bryan Cranston) and his partner Jesse Pinkman (Aaron Paul) as they face repercussions from drug kingpin Gus Fring (Giancarlo Esposito) for killing Gale Boetticher at the end of the previous season. Meanwhile, Skyler White (Anna Gunn) breaks into her husband Walter's condominium to investigate his sudden disappearance, and Marie Schrader (Betsy Brandt) struggles to help Hank Schrader (Dean Norris) recover from his injuries.