Is overextending the biggest LoL mistake people make?

Getting caught out and overextending imo

Overextending is basically the game's bread and butter. You don't get caught out unless you're alone, and you're only alone if you've overextended. Whether that's pushing past your vision or walking a little too far away from the group, same principle.

overextending is something that is a lot harder to fix than anything else because there are times in which you are doing it on purpose so your team can get something on the other side of the map other times it's you missing that one skillshot (and in some times actually landing said skillshot) that causes you to overextend for that kill. People get tunnel vision on something for a split second and then before they know it they are overextended. The game is essentially you constantly taking risks so you can get some form of reward (cs, kill, objective) so overextending is something everyone will keep on doing no matter how good they are at the game until a way to play the game perfectly is found in which case the game will either stagnate to oblivion or change immediately

Its not necessarily the biggest in terms of game impact but it is likely the most common.

Overextending or overstaying

It's a big mistake a lot of people make, but it's really team grouping that's the most common. If your team doesn't group on objectives, you tend to lose against the team that does. This includes pushing, dragon, etc.

Tbh playing too aggressive and underestimating damages is the biggest mistake.

I think if you have vision and map awareness, you can get away with it. So I'd argue the answer is lack of situational awareness.

Yup. Basically. Especially split pushers.

That's definitely one of my biggest screw ups.

I usually am very good about bwing cautious, but getting too cocky on a squishy champ that can't fight close up will very quickly set me straight.