Difficulty is an option in some single player/co-op modes that allows a player to adjust the game after one's skill. In the most cases, there are five difficulty levels. Depending on what mode is being played, different difficulty levels will affect the game in different ways. For example, a higher difficulty level in the Subspace Emissary will make the enemies harder by giving them more HP and making their attacks stronger, while a higher difficulty level in Target Smash won't affect the characters' properties at all, but instead change the stage's design into a more difficult one. Sometimes, unlockables such as trophies or stickers depend on the difficulty on which a game mode is cleared. In the Subspace Emissary, Stock Balls vary in number, from appearing in most levels in Easy to never appearing in Intense.
In Smash 64, the difficulty setting is only available for the 1P Game. In the other three games, the setting appears for the Classic Mode, Adventure Mode/Subspace Emissary and All-Star Mode. Additionally, in Brawl, the setting is available for Boss Battles, and has been added to Event matches and Target Smash!!. However, the event matches in Super Smash Bros. Brawl and Super Smash Bros. 4 only have three difficulties (Easy, Normal, and Hard).
In Event Matches, only three difficulty levels are available: Easy (blue difficulty), Normal (green difficulty) and Hard (yellow difficulty).
Difficulty levels were significantly overhauled in Smash 4. The game's retooled Classic Mode features the Fiend's Scale to determine the game's difficulty. In this system, the player is able to select an intensity from 0.0 to 9.0, with higher intensities leading to harder fights, but more rewards; the default intensity is 2.0, and selecting other intensities requires some coins, with each .1 increment costing the player a set number of coins depending on the intensity.
Every time the player loses, he or she is given the option to continue. If the player elects to continue, the intensity lowers by 0.5. Regardless of whether or not the player continues, some rewards attained in the Classic Mode will be lost, as will some coins on the Fiend's Scale. The system is essentially identical to the Fiend's Cauldron intensity system from Masahiro Sakurai's previous game, Kid Icarus: Uprising, including the same titles.