Usually, "peer reviewing" code is the best way to create a lot of enemies. Very few people on average like people reviewing (and criticizing) their work - unless working in environments were that's enforced for some reasons. I had many issues while pointing out bad code (and thoroughly explaining why it is bad, with a lot of references to books, best practices, standards, etc. etc.), or looking like the one who likes to put others into bad light, up to the point I was recalled by HR telling me explicitly "you need to learn how to relate to people properly" AKA don't "annoy" anybody and who cares if a lot of crappy code goes into production, HR doesn't care as long as it's not an HR issue.
All I wish is to avoid that, because when the fans start to throw s**t around, it's not usually the "original developer" who is called to fix things quickly, and calm an angry and unwillingly to pay customer, but me, and I'm quite tired to fix someone else ugly buggy code - often needing a complete rewrite in a too short time.
Lately I stopped reviewing completely, leaving that code entering production. After a while, I was even asked "please, oversee X to ensure he doesn't create troubles", and my answer was "I have my own tasks to finish. I have no time to babysit anyone. And if I advise him, he doesn't listen, is piqued, and then complains to HR. Choose: we get rid of X, and I write the code when I can, or he writes the code but I won't accept any responsibility of it, nor I'll babysit him". After a couple of times they choose solution 2, and customers were not happy at all, and s**t started to hit someone above me, a couple of developers were moved to other roles...
Also in many software companies that have promotion states, those reviewing the code before accepting into an "higher" branch are not usually those who have the expertise to properly review it. It may happen in some notable projects like the Linux kernel, but in other situations they are often less skilled devs (or even testers) checking only if the code does pass tests.