In a group of angelfish [I assume your angle was meant to be angel
] the males will be territorial toward each other. One will become dominant. Initial stages will be one male turning toward another and after a period of motionless (from both, unless the other backs off quick) moving directly at the other. If the other again doesn't back down, they may nudge one another, either on the side or face to face. Lip locking can occur.
If the dominant male is particularly so, in fact a bully, this behaviour can extend to all the other angels, male and female. Sometimes a single fish may be targeted. In either of these scenario, f they have insufficient space to escape, they will weaken to the point where they may remain "hidden" and even refuse to eat. Death is not far behind.
Stress is obviously being inflicted on the subordinate fish through all of the above. In a tank of sufficient size and the proper environment, and provided there is no "bully" male, this will not lead to anything serious. It is natural behaviour. I have watched a group of 10 or so Pterophyllum scalare in a very natural exhibit at the Vancouver Aquarium; the tank is about 8 feet floor to ceiling, 5 feet across, and several feet depth (front to back). The angelfish are always in a group, spaced out, around some branches. The male dominance described in my first paragraph is fairly continuous. I have never seen any physical interaction. The targeted fish simply turns slowly and swims a few inches, and the dominant moves elsewhere. This is how it should be.
As for signs of stress, this is not always easy at the initial stages. As I mention in my article on stress, it can be un-noticed by the aquarist until it is too late. Rather than repeat all that, here is a link to the article: http://www.tropicalfishkeeping.com/f...um-fish-98852/