LOL lvl20-29 abyss is always the problem huh? There seems to be the most amount of rude annoying people killing others with no reasons (even if they had one, it would be unreasonably stupid XP)...it's worst in lvl20 abyss...a little better in lvl30 abyss, but there still are people like that...and then it gets better from lvl40 abyss. Haven't been to lvl60 abyss yet, but I can imagine that place being quite peaceful.
But yeah...be careful of those rude people. If you see signs of some of them staying near you, to try and think of an excuse to attack you, and try to kill you, just kill them before hand. It's always better to begin your attacks first...If they tried to attack you, they deserve to be attacked.
Watch out for mages, they're the deadliest when they start to attack you first D: