In League of Legends, in matches where the skill levels of both teams are equivalent and the game is balanced, the team that makes fewer mistakes will have a higher chance of winning. However, there are also critical mistakes that, once made, will lead to an “instant defeat,” leaving almost no chance for recovery.
Here is a list of mistakes to avoid:
Grouping Up Closely Even When the Opponent Is Strong in Team Fights
Even if your team has a significant advantage over the opponent in terms of gold and items, positioning during team fights is something that cannot be overlooked. In a team fight, if just 3-4 members are out of position, the entire team can be hit by a devastating wombo combo from the enemy team. After losing that fight, the opponents often have many options, such as taking major objectives or ending the game if time allows.
Going to Ward Alone in Areas Without Vision

Everyone agrees that vision is crucial, but controlling vision is even more important. When you venture into areas without vision alone, you might encounter all 5 enemy team members lying in wait, leading to an immediate “death count.” Making a mistake and getting killed like this usually costs your team a Dragon or Baron, and in worse cases, the entire game due to being outnumbered in fights.
Focusing Too Much on One Thing

Too much of anything is not good, and this applies to League of Legends as well. For example, if you focus too much on farming minions and forget to ping when the opponent roams, or if you concentrate solely on poking the enemy while neglecting the minimap,… If you don’t want to be drawn into your opponent’s playstyle, you need to distribute your focus across all important factors.
Not Understanding Your Role in the Game

In each different team composition, each champion has a different role. For example, Tahm Kench in Team A must always stick with teammates to initiate fights with his ultimate, but Tahm Kench in Team B needs to stay close to the AD Carry to provide protection at all times with W. Not knowing your role in the match is akin to not knowing the conditions for winning. Therefore, it’s crucial to clearly define your role to maximize a champion’s strength and avoid getting “lost” in the game, leading to unfortunate losses.
Not Knowing How to Leverage Your Team’s Strengths

Depending on the location, time, and situation, each team composition has certain strengths. For instance, a poke composition with Varus, Nidalee, and Jayce should gradually poke down the enemy rather than engage in quick skirmishes. Or when two teams split, with one team taking Baron and the other taking the Elder Dragon, the team with Baron should push waves without fighting and wait for the opposing team to lose their buffs, while the team with the Elder Dragon should force fights instead of splitting push against the enemy team.
Being Affected by the Opponent’s “Taunts”

Many players often fall prey to the enemy’s “all chat taunts” or annoying emotes, causing them to lose their cool and make very basic mistakes. The simplest way to resolve this is to mute all chat and disable all enemy emotes.
Winning a Fight But… Doing Nothing

This often occurs in lower ranks, typically when wiping out the enemy team opens up opportunities to take towers, secure dragons, claim Rift Herald, or steal buffs,… but your teammates choose to back off to heal. If you don’t capitalize on your advantage by securing resources on the map, at any moment, the enemy team can turn the tables in an instant.
Buying the Wrong Items at the Wrong Time

Having more gold than your opponent is not very useful if you don’t use it effectively. First is building the wrong items; each champion has different build paths for different situations. If you stick to one build for all matches, it’s hard to avoid being “crushed” by the opponent. Secondly, timing is crucial; you need to build counter items early so that the enemy doesn’t become too strong. Waiting until the enemy gets strong to build counter items is too late, and the effectiveness of the items diminishes significantly.