Since it is a mode that heavily relies on “luck,” players in Teamfight Tactics often encounter extremely frustrating situations, making it hard to keep a “cool head” to calculate their next moves in the match.
Here are some of those annoying situations:
Encountering “extremely lucky” players

In Teamfight Tactics, sometimes you can meticulously arrange your pieces, pick counter items, and calculate everything in detail, but all those efforts can go to waste if you face an opponent who is just too lucky. For instance, having Garen in round 2-1, or a 2-star Gangplank at level 7,… In such situations, many players often opt to continuously “Ping ?” on the enemy’s board to vent their frustration.
Getting “ks’d” by a strong composition right from the start

Shredder Xayah is currently a hot composition, as it is easy to play and set up, so quite a few players choose it. However, even though Xayah is a 1-star champion, she can still be “ks’d” if everyone decides to play her. This situation causes many players to “die together” as they all insist on following the same strategy and refuse to change their composition.
Situations of “having everything but missing you”

Many players call this situation “being baited,” because sometimes key champions do not appear on your board at all. For example, in the early rounds, you might have a plethora of perfect champions for a Cybernetic build like Leona, Fiora, Lucian, Graves, Vi, Ezreal,… and decide to play this composition, but ironically, even after rolling at level 9, you still can’t find Ekko, leading to an incomplete team and falling out of the top 4 in frustration since changing your composition is now too late.
Items drop that are completely unrelated to the composition

Playing a composition where the pieces appear without needing to roll is a very comfortable feeling, but when every time you fight monsters the items dropped are unrelated to your composition, it becomes extremely frustrating. Imagine playing a Mage build but the monsters drop only BF Swords, or when playing a Brawler Gunner and Kayn drops a Black Mist Heart,… these are all incredibly frustrating feelings.
When you are “losing health” but encounter a stronger “losing health” player

Many players often choose to arrange weak pieces to create a losing streak to earn money or items, but sometimes they encounter someone who shares the same mindset, and that player is even better at “losing health,” forcing you to win and lose your losing streak.
When you need items but the monsters drop only “coins”

Each monster round gives you a chance to receive great items for your composition, or sometimes you need any items when playing Cybernetic to activate the passive to become stronger. However, the result is that in a monster round with 6 monsters, only one item fragment drops while the rest is all gold, causing your main carry to not gain any strength at all.
When you have Neeko but can’t use her

Because the rules of Teamfight Tactics only allow a limited number of each champion to appear on the board. So sometimes you have 2 2-star Jinx, 2 1-star Jinx and want to use Neeko to get a 3-star Jinx.
However, the result is that there are already 4 1-star Jinx somewhere on other players’ boards, so you can no longer use Neeko, and can only wait for those players to “fade away” or sell Jinx. This situation can sometimes lead to unjust losses because you couldn’t upgrade your strongest carry to 3 stars.