If you've ever played any kind of multiplayer game for more than an hour, then you're probably familiar with the concept of something feeling overpowered (or OP, as most normal people refer to it). Usually, this feeling stems from seeing something perform better than expected, almost to the point that it seems like it completely ignores personal skill. In most shooters, it's often a gun, in MOBAs or games like Overwatch, it's typically a specific character; even card games like The Elder Scrolls: Legends have cards that can be considered wildly OP. In fact, it is almost impossible to find a multiplayer-centric game whereby an element of the game isn't considered OP and unfair, especially given how quickly information can travel thanks to social media and the internet in general.
As an example, you can take a look at Overwatch, a game that has received at least one balancing update every couple of months (which are seemingly based on community feedback). Within the first couple of months of the game's release, people were claiming that Widowmaker was incredibly overpowered and so on and so forth, prompting Blizzard to reduce her rifle's base damage by 20%. Of course, it seems like a rather unnecessary change now that most people are familiar with the core mechanics of the game, but it just goes to show how quickly people can claim that something is too powerful. Even as recently as last month, there was a very vocal group of people who claimed that Sombra was going to destroy Overwatch's balancing before she was even available to the public; now Sombra is generally considered to be one of the most inconsistent and ineffective offensive heroes in the game. As it turns out, a hero whose abilities only make a noticeable impact against a very specific group of enemy heroes isn't as insanely powerful as everyone feared, especially when you must coordinate with your team to take full advantage of Sombra's abilities.
Similarly, one of the Titans that you can choose in Titanfall 2 is Tone; popularly recognized as being extremely powerful (or at least that's what the more vocal segments of the game's audience believes), with some claiming that Tone is oppressively strong when compared to all the other Titans that are available to you. Naturally, very few also care to point out that Tone's loadout is essentially comprised of a mix of various weapons and abilities that are available to you in the first Titanfall, which no one really complained about.
Thus, the inevitable question must be asked: what makes something OP, and how can you objectively claim that something is OP when there are so many variables to control for? Is it possible that because Titanfall 2's Tone is so similar to the Titans in the prequel that veteran players (who, by virtue of having played the first game, would be more skilled than someone who didn't play the first Titanfall) would naturally gravitate towards something that they are familiar with, thus making Tone seem unbeatable? Or perhaps the nature of Titanfall 2's maps just naturally benefits Tone's intended playstyle? There are so many variables that it would be impossible to set up a controlled environment that also emulates your average multiplayer game.
Naturally, there are also some cases where things can be legitimately OP. In Destiny, Thorn and Shotguns genuinely negated any other playstyle because there really is no reliable way that you can counter someone in that game who can either instantly teleport to you and instantly kill you, or land two lucky shots while you get poisoned to death at virtually any range. Going back to Overwatch, McCree was intended to be an anti-flanker, but his Fan the Hammer ability used to let him kill almost any other character in the game with no actual counter other than "Stay 100 feet away from him." In a somewhat ironic twist, McCree was then balanced in such a manner that he was harder to use at close range, but could snipe people across the map, before he was balanced to the state he is in now. In such cases, yes, you can easily point out that something is blatantly overpowered because everyone would (if given the chance) pick that character or weapon for almost every situation even if they don't like doing so, but these are more extreme cases that typically don't really require any kind of debate.
As you can probably expect, there are and will be plenty of other games that will have elements that are considered overpowered, especially if a game is updated with free and new content in a manner similar to Overwatch. However, it should be kept in mind that it is almost impossible to perfectly balance a game. No matter what, people will find ways to be the most efficient or best at something, which in itself is highly dependent on individual skill (something that has such extreme ranges that you may as well try and figure out how to clone people if you want consistent teammates). On top of that, personal pride will almost always tempt people to say that no, it's not possible that that "noob possibly beat me other than because he's going Easy Mode." In any case, perhaps it is for the best that Blizzard's balancing strategy with Overwatch is to (seemingly) subtly nudge people towards using different heroes every few months. After all, why bother pursuing actual perfect balance when you can simply give the impression of perfect balance instead?