That sucks. Some people legitimately can’t be vaccinated because of medical reasons (which is why those who can, should, to build herd immunity), and in most cases receiving the vaccine causes mild flu-like symptoms. But there are reports of rare, more serious reactions as well like your friend’s.
For me, the first shot did nothing except very mild soreness at the injection site and the second caused fever and aches and pains for a half a day, most of which I slept through.
In almost every case, coming down with a full-blown case of Covid is worse than getting the vaccine, and can be much worse — that’s kind of where I fall on this.