I was having the same issue, and one of the answers in here helped me, but not for the reason explained so I thought this might be useful for others.
Some plugins might depend on the version of vim, and may work in version 7 but not in version 8, when you install MacVim this could be version 8, and the terminal vim version might be 7, both will use the same .vim folder and .vimrc to load the plugins and configuration, when you open the vim from terminal it might still work because the plugins were depending on vim version 7, but when you try to execute MacVim it will try to load the plugins using version 8 and then it will crash, the reason some of the answers worked it's because they are replacing the system vim, therefore MacVim and vim will be in the same major version, if you have upgraded from the previous version the best you can do it's to clear up the plugins folder and then load MacVim or vim and check that everything is working, then start applying the plugins one by one checking that they are not breaking vim. At least with this method I found that one of the plugins was not working as expected and removing it solved the "MacVim" issue.
In summary:
- move your .vim as .vim_bak
- move your .vimrc as .vimrc_bak (suggested by @hai feng kao)
And test if this solves the issue, if that's the case then a plugin is breaking your installation and you will need to activate some and figure out which is the one that causes the issue.
Hope this helps to others, I've followed a lot of these recommendations without success until I decided to upgrade vim (terminal) and this started to break as well, that pointed me in the right direction.
Again hope this saves some hours for some.