I could see if people where shooting shotgun shells out of longuns or they run around with a x above there head. Or the fact of some killing u with laggy bullets after u have alreay killed them. But most my games is because most peoples aiming just sucked during the time.
If I don't like that they killed me, they must be a lagger. If they're just legitimately doing better than me, then they must be trying too hard. But if they are doing worse than me, they're just some stupid noob. DON'T YOU GET IT? IT'S ALL ABOUT ME!!! That's the way it works and I don't think it'll change anytime soon.
But seriously, I'm not entirely sure who you're talking to specifically. Lag is a real problem. Now it's extent may be exaggerated but other times it might be overlooked. But most importantly (to address your post), I wouldn't cry "lag" if I lost a 1v1. But is some guy is skating across the map, teleport meleeing, pulling me down long after I jumped, or anything of the sort they might be lagging. Whether or not my aim is on isn't a deciding factor to whether the match is laggy.
Now, a lot of noobs who play UC3 are just really bad aiming, and they probably don't even know what "lag" is. I don't think they even know they're doing bad, so they probably don't need something to blame it on.
Maybe you have a bad connection and that's why they are missing you
I've seen countless players from countries known to have a terrible connection quality and I shot them right in the chest/head but no hit would count. Then they kill me with just a few bullets.
When I'm shooting a "five bar" player I kill him in no time and even if my aim was off the stupid aim assist would do it for me
After playing this game for a while you can often tell the difference between a player who's better than you and a lagger. Whether you want to admit that someone's better than you or not is a different story.
I say it's lag more often than it isn't. This game loves lagger