Amok is the 21st-century standard spelling of the word meaning (1) in a frenzy to do violence, or (2) in an uncontrolled state. Amuck is an old alternative spelling of the Malaysian loanword, and it had a few decades of prevalence before the middle 20th century, but it has now fallen out of favor. A few usage authorities still recommend the latter spelling, but amok is preferred in edited writing of this century.
I also love running amok at De Kaaskamer, the ideal spot for a tour of Dutch cheeses. [NY Times]
Images of drunken language students running amok on Malta’s streets and having sex on the beach made headlines last summer [Guardian]
Most of the commentary has been to the effect that this is an example of the nanny state run amok. [Wall Street Journal]
As a teenager, he endured his fair share as he ran amok with his mates. [The Australian]
This Ngram shows that amok became the standard spelling around 1950 and now prevails by a large margin: