I might slice my wrist
Or pretend like a vulture and drop off this cliff
With the use of “pretend” he implies that although it may sound like he’s willin' out, he is in complete control of the situation. A vulture usually circles dead animals — it might jump off a cliff only to gain the speed necessary to attack.
Dark nights like this/slice my wrist/drop off this cliff are all very morbid and makes Kendrick sound suicidal. As he said, he carries “traits of a traumatized soldier” meaning he’s unpredictable and one day might be confident enough to kill you, while another may be very suicidal. The catch in this string of lines is that he makes like a vulture, meaning that when he jumps off a cliff to his apparent death, he actually is just gaining speed to fly higher and attack.
Possible reference to Batman who is often referred to as the Dark Knight. He tends to drop off of places to then glide in order to target his enemies.
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