Almost immediately, outrage swept the Internet. See, this wasn't just any lion, this was Cecil, a lion so popular and beloved that most of Zimbabwe had never even heard of him. Nevertheless, the rest of the world lost their shit. Sure, some of that had to do with the fact that Cecil was living in a wildlife preserve and was apparently lured into leaving its boundaries solely so killing him would be technically legal, but it was mostly just that we were told this lion was famous and that Walter Palmer was a monster for making him a trophy.
The calls to bring the people behind this illegal hunt to justice soon became deafening. In some respects, it worked. The guide Palmer hired to keep him within the lines of the law was charged, as was another guide who was responsible for the killing of a different animal months earlier. What kind of actual punishment they'll face remains to be seen, but still, at least that happened.
As for Walter Palmer, he didn't face any charges. The job of a guide is to make sure hunters stay within the limits of the law; his guide essentially failed him on that front. There's not much the courts can do. However, that doesn't apply to the court of public opinion. In that forum, Palmer has been absolutely shredded. Sure, he eventually returned to his dental practice after months of uproar ...
Come on, man.
... but it's apparently open only one day a week, which I learned from the business' perpetually defaced Yelp page. Things have gotten so bad there that Yelp has apparently hired a team of people just to keep watch over Palmer's page for reviews that don't actually relate to the business, and they aren't even sort of capable of keeping up with the torrential downpour of hate that's besieged the page in the months since the scandal broke.
You're fighting a losing battle.
So, that's cool. Looks like you won that war, Internet. Your efforts have effectively ruined the life of a lion killer. What those efforts haven't done is stop lions (and any other wild animals you can name) from being killed for sport and profit. Yes, Zimbabwe imposed a ban on this type of hunting in the days after the story broke, but they lifted that ban less than two weeks later.