Mac freezes after login
Sadly, this is a very broad issue, and unfortunately it's difficult to solve over the internet with so little information. I'll give as much help as I can, but you're probably best following online guides until you can come back with more information. MacWorld has a good guide, as does HowToGeek and a host of others. Given what you've done so far, I'll try to help, updating this post as you complete steps. Comment and let me know what the results are.


First, let's run Apple Hardware Test or Apple Diagnostics. This will help us find out if your issue is hardware or software based. If your mac was made after June 2013, use Apple Diagnostics. Otherwise, use Apple Hardware Test. If this fails, you're probably in big trouble (although it probably won't.) Best case, you simply don't have it installed for a variety of reasons. Normally, if your Mac is new enough (again, almost certainly), it'll automatically start using internet based AHT. However, if it didn't connect (or can't) connect to the internet, you might be able to create a bootable version of AHT on an external drive. Follow the instructions here and see if that works.