The KSG is not gonna be complained about at all. Will it be one of the better shotguns to use? Sure. But it's a freaking pump action single slug skill weapon, that needs to be ads'd and aimed right on target to get the OSOKs.
lol.. If M27 is a 4 hit kill, it would be far from OP, since it has one of the slowest kill times(4 hit kill at 720 RPM). Even the M4A1 in COd4 and MW2 killed faster(4 hit kill with almost 900 RPM).
Less is more. Everything you want, isn't everything you need.
In all seriousness though, the Ballista w/iron sights. It is going to be called "OP" by the little kids and "1337 QwU1k5c093rz" because the former will be unable to kill a skilled person who uses it, and the latter will complain because they can't use it to quick scope and will call anyone who uses it properly (as in uses it for mid to long range combat) a scrub/[explicative(s) removed]/hacker/cheater/loser for using an "OP" gun.
"The faster I run, insanity can't catch me!"-Lanipator "An arrow piercing a knee is no laughing matter."-Malus_X6