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Every f*cking champion uses it . I can list the number of champs that don't it one hand , maybe . It's supposed to be a spell for champions with no mobility like jynx , but every almost every champion uses it .

Who doesn't use it ?

Yummi

Yi ( sometimes)

Trynadere ( sometimes )

And ... We are done !

If there was an item that most of the champions in the game would always use , I can guarantee you that people will say it's broken , but flash is used on almost every champ , yet still not nerfed / alternatives get added / buffed ( sprint , protobelt , maybe a league PC item / spell ( I don't play the game ). Anything . This spell is broken . Even limiting it to ranged champs only can work .

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over 2 years ago - /u/R0gueFool - Direct link

So it really comes down to how you want to categorize Flash, yes when compared directly to another summoner spell it is very strong. However, we like how Flash shapes the game so we don't treat it like other summoner spells, and instead think of it as a default tool each champion has access to, and some (like you said with Yuumi) will opt out of it. This is why you see it in every default loadout (other than Yuumi).

This means it isn't just for low mobility champions, but a tool for all champions. Maybe that is safety in the laning phase before they get their mobility, or as a tool to make plays later in the game. But you are right that it is a very popular, basically mandatory, summoner spell.