Fizz has always been a little bit of an odd champion in League of Legends. If things are going well for him, he’s very likely to one shot the squishiest member of the enemy team. If things are going poorly, however, he might as well not be in the game at all. It’s a huge swing from good to bad that has always made him a little tough to balance.
As for how exactly this happened, most of it has to do with the way his W, Seastone Trident, interacts wit the rest of his kit. It’s generally just an empowered basic attack, but when you add in the mobility of his Urchin Strike and Playful/Trickster, he gets a little too tough to handle for most squishy champions. So Riot is once again trying to get a handle on its Fizz problem by adjusting what his W does.
The first time Riot did this, they added a delay to the ability, meaning you had to hit the enemy with your empowered attack at the right time, or you wouldn’t get all the bonus damage. While that worked well against champions, it never quite worked against minions.
With his new and improved Seastone Trident, Fizz shouldn’t struggle against champions or minions. The ability grants Fizz one empowered attack and if the attack kill his target, the ability ends. If it doesn’t, then he gains slightly empowered basic attacks for five seconds. These attacks also do on-hit damage.
All this really means Fizz will still do some empowered damage with his W, but not quite as much as before. On the other hand, if he doesn’t instantly kill a target, he’ll now have a much better chance of finishing them off.
While this isn’t necessarily going to completely fix some of Fizz’s more burst-oriented problems, it should at least make them a little easier to deal with in-game, while also making the champion as a whole a little easier to balance for Riot.