Griefing

Griefing is the act of intentionally ruining other players' experience with a game, essentially trying to cause them grief. Seen in essentially all multiplayer games, especially those playable online, it entails a variety of acts aimed to deliberately agitate, make the game not fun, or make the game outright unplayable, for opponents and teammates alike. This includes the  series.

Methods of griefing
What exactly is considered griefing is nebulous and nuanced, as different people can get offended and upset about different things. Consent and expectations also color this conversation, to the point of situations where attempts at griefing fail due to the victim not caring or players unitentionally griefing someone without realizing.

That being said, common methods of griefing are as follows:
 * Self-destructing repeatedly and using share stocks to deprive others on the team of their stocks.
 * Constant use of team-damaging moves, such as many explosives, simply to damage teammates instead of the opponent.
 * With team attack on, intentionally attacking teammates.
 * Ganging up on another player in a free for all.
 * Deliberately attacking one specific player and, once they're out, either acting friendly with others or making no attempt to battle with anyone else.
 * Simply being useless, such as not remaining idle or doing nothing but taunting.
 * Continuously using loud taunts or taunts that get annoying with repetition (Such as Captain Falcon's down taunt or 's up taunt) to throw off or annoy the players around them.
 * Crouching repeatedly (commonly known as "teabagging").
 * Choosing an abnormally large stage, such as Temple or a large Custom Stage, often in combination with a fast-moving character like Sonic or Fox, to constantly and safely run away from the opponent until the timer reaches zero.
 * Abusing tactics that make themselves very difficult or outright impossible to hit at all, such as the Infinite Dimensional Cape with, shell hopping with , and other such stalling tactics.
 * Deliberately playing online with an awful internet connection to subject players to extremely laggy matches.
 * Interfering with their own internet connection on purpose, such as by applying tin foil to the router or rapidly moving the Nintendo Switch around if it's in Handheld mode, in order to create lag and throw off the opponent. Commonly known as "lag switching".
 * Employing hacks to desynchronize online participants or play as an invincible character, such as Giga Bowser or Wario-Man.
 * Repeatedly using Pokémon Change with the in online play to lag the game (although this does not work as effectively in Ultimate, where the switch between Pokémon is much faster).
 * In online play on Smash for Wii U, changing their name tag to something insulting or otherwise offensive, and optionally proceeding to play using the new name.
 * Quickplay in Ultimate can be subjected to its own specific forms of griefing:
 * Purposefully disconnecting from an online match by closing the game when they're about to lose, so their opponent doesn't gain any GSP for beating them.
 * Intentionally tanking one's GSP so that they can then get matched with worse and more inexperienced players that reside in much lower GSP ranges.
 * Deliberately using nonsensical rules, like running three stocks with an abnormally short time limit and relying on either timing the opponent out or winning via Sudden Death. One can also run more casual-oriented rules, such as having items enabled and all stages available, with the intention of griefing competitive players, particularly in higher GSP ranges where such players largely reside, though it's ambiguous when players are running such rules with that intention or because they legitimately want to play with those rules.
 * In early versions of Ultimate, the Special Flag was an individually toggleable item for Quickplay. This resulted in griefers running rules that had only the Special Flag enabled, often in combination with Stamina, causing matches where eliminating the opponent's stocks was nigh-impossible and so guaranteeing every match going to time out, while radically changing the win condition of the match to become "who can get the most Special Flags". Version 3.1.0 would remove the option to toggle Special Flags in Quickplay to prevent this.
 * In Ultimate, Battle Arenas are also susceptible to their own specific forms of griefing:
 * Going into Arenas with competitive rules and where the option for players to choose their own stages is enabled, then deliberately picking a non-competitive stage, especially one that enables circle camping.
 * Joining an Arena with a 2-player limit, and then deliberately staying in the Waiting Area or the Spectator Stands instead of entering the ring, forcing the Arena host to kick them. This can be attempted with larger Arenas to take up a spot, but as long as one other player is able to join, it doesn't completely prevent any matches from happening.
 * As the Arena host, kicking a person mid-match to force all players back to the arena. This can be extended to abusing their kicking powers in general, such as kicking someone right as they get into the ring after waiting a long time, or kicking people to bypass the queue to immediately get back into the ring after losing.
 * If enabled, playing loud sounds or music over the Voice Chat in Arenas to annoy players or cause voice chat lag, known as micspamming.
 * Ultimate's Stage Builder can additionally be susceptible to its own forms of griefing, when posted via Shared Content:
 * Using offensive words, or slurs not already disallowed by Ultimate's Shared Content filters, in the name of one's stage or within the stage itself, or naming stages after inappropriate actions with the intent of causing shock or discomfort.
 * Creating stages that are sexually explicit or feature potentially sensitive content.
 * Creating stages that employ multiple moving parts or explosions and portals to cause a large distraction during a match.
 * Stages made to promote third party services or content that could be potentially harmful to use or see.
 * Using hacks or exploits to bypass the build limit set by the Stage Builder engine, and creating a stage with the purpose of causing the game to lag or crash.
 * Reporting another player for no legitimate reason, or for simply losing to that player.
 * When Miiverse was active, sending a player a friend request attached to an insulting message. In Ultimate, they can instead send a friend request over the Switch's friend system while changing their name to display as an insult or something else offensive.

In competitive play
Griefing has occured many times over the years at all different levels of competitive play. Players intentionally use cheap tactics or otherwise annoying actions to frustrate their opponent into making mistakes or giving up entirely, ensuring their victory. However, the level of malice in these situations is not equal every time, as some cases happen between friends who all understand everything is in jest and will not take it personally. There is typically no specific rule that disallows griefing, as that would be difficult to enforce, but some tournament organizers are known to issue warnings about griefing before disqualifying the player on a second offense. Some forms of griefing can be considered cheating as well, and are punished accordingly.

Griefing was especially common in Basic Brawl, as the combination of anonymity, complete lack of control over the match rules, free-for-alls being mandatory, and no restriction over stage and item selection, created conditions unfavorable for serious matches that were ripe for griefers to abuse. This is one of the main criticisms players had of Basic Brawl, as many found it unenjoyable for those choosing not to resort to griefing themselves.

Smash 4's griefing scene was far less rampant, but still was common enough in For Glory, which was intended for serious matches. Unlike Brawl's Wi-Fi mode, which was entirely unmoderated, the system in Smash 4  allows the reporting of griefers, which can result in them being sent to For Glory Hell. Additionally, they could be blocked via the Wii U's built-in friend system, which would indefinitely prohibit them from matching with players until they were unblocked.

Griefing persists in Ultimate, but its impact can be better mitigated, through the better reporting system, and with players being able to block anyone they play with, which will then prevent them from being matched together on Quickplay and prevent each other from joining their Battle Arenas for the duration of the block.