Like Super, I feel incredibly sorry for his family but somewhat conflicted about him personally.
He gave thousands of pounds to the most abusive regime in the world, because he fancied a fun holiday somewhere exciting. Something to make his frat brothers go, wow, cool, Otto went to North Korea. Did he see a Vice documentary and think, ooh, I'd like to check that out?
The money he gave directly to the Jong regime props up concentration camps. His presence (like the presence of every Western tourist) is a propaganda coup for them.
I hate that the money he gave them was used to imprison and hurt him. But who does the regime usually hurt? Some poor peasant with the bad luck to be born 20 miles the wrong side of the DMZ, who hoarded an extra ration of food to stop his children starving to death (as thousands of NK children are)? Someone who accidentally reported an inconvenient economic truth? Someone who told an off-colour joke about the Kims?
None of these people chose to live this way. Warmbier did. He decided to visit and give money to a country that treats people that way. And I'm not going to feel any sorrier for him than I am for the thousands of people who have been brutalised by the DPRK when they would have given anything for a fraction of the opportunities he had.
For the record, I don't believe he did anything "wrong" while there - perhaps he engaged in a fratty "prank" of trying to steal a sign. (And if he did, he put a half a dozen innocent lives at risk). But I honestly doubt it - I think NK officials thought there was a CIA operative among the group, and thought he might have been it, and once they detained him, things just spiraled. I also think he was probably killed accidentally - I think he became hysterical after the trial, when he realised his release would be a matter of years, not days, and they overdosed him on sedatives.
Ironically, if he actually had been an agent of the CIA, I'd feel totally differently about him. Spying on the regime is a legitimate reason to be in North Korea. Wanting a cooler holiday than all your fellow students is not.