Well in X5 i know that sigma is Fast, Strong and efficent.
Sigma his very smart it s the whole point of him being a virus !
Sigma can fly and teleport ! He can also charge in any direction among some other attack i dont remember. There is also his last form where his body is so big that you can only see his fists and head ! The fist keep attacking they have spike on themself to crush their enemy and the hands can open to start shooting ! The head can shoot his little attack ! Even if Seymour low dodge can manage to dodge the 4 and thats unlikely they will after a few sec go attack attak homing for Seymour and i doubt he would be lucky up to 3 time in a row ! His first can be destroyed yeah ! But he repair them very quickly and when his fist are not destroyed half the time he use his ability to not be able to get hit !

Seymour is gone !