Complex sentence: Perhaps ironically, veteran riflemen are virtually the direct opposite of newbies described above, in that they characteristically are competent in virtually every style of paintball play, travelling by themselves, instead of moving with other riflemen in a squad.
Split into simpler sentences: Perhaps ironically, veteran riflemen are virtually the direct opposite of the'newbie riflemen' described above, in that they characteristically are competent in virtually every style of paintball play. These riflemen would usually travel by themselves, instead of sticking with other riflemen in a squad.