I play support mostly, so I really only know how to deal with Garen during teamfights. Basically, when you see him running at you when he uses his Q, you can slow him all you want because now his slow remove is gone. Then when he does silence whoever, he's right in the middle of your team, and either that's the enemy team's initiate or Garen is attempting to poke. If it's the first, he's going to use his W and E shortly after, so you actually don't want to attack him. This is the time you focus their squishies. Soon as he stops spinning to win, he's either going to be easy to kill if he built damage, or he's not going to do any damage if he built tank. Yeah, his dunk is nasty, but someone on your team should have their CC back up around this time (After killing their heavy damage), and you can stun/cc him and kill him. Basically it changes around your prioritization list. It goes like APC-ADC (You may swap these depending on which is cranking out the most damage), Garen, Support, and then finally Tank.

the problem with garen isn't the laning phase, landing against him is easy enough. the problem is once you get in to team fights, garen is able to run up to the adc use his e, and then basic attack basic attack ult and the adc is out of the fight or dead. ik the adc can get a ga, but it takes the adc, and a support and/or junglier just to peel for him to get garen off, which leaves the rest of the team to fight. garen just needs to be more balanced, he does too much damage for the amount of damage items built. my build is boots, black cleaver, warmongs, sun fire, frozen mallet, and last item is tanky, but depends on the other team. I've played as and against garen and i strongly believe that he is too strong. and the only reason why he is op is because for 1000-1300 elo players is because no one knows how to peel, which is why he doesn't see tournament play. unless riot wants to make garen a viable tournament champ i don't see how a nerf on him will hurt because the majority of players are 1000-1300 and are getting smashed by him

Usually nidalee can take care of him by just spearing him when we wants to farm. Trap the bushes by the dozen so he can't just bush heal/gank and end's up taking all the traps damage and then when you poke enough go cat form and tear him up. Usually it get's so bad for him that he needs to call in a jungler because he can't handle Nidalee. Good times.

In team fights, as Nid you just poke him up and if he runs towards you then pounce away. He cannot catch you.

lately bruisers on the tankier side have been getting rewarded this season with the new items

garen is a prime example, as well as darius, olaf, and even ww.
it's because of items like warmogs that make them indestructible, while they still have a high damage output

Solution
-Build Warmogs + SFC
-Build IE, BT, Cleaver
-Deal ridiculous damage with your E to everyone on the enemy team
-???
-Profit

his ult is even stronger than elise spider from Q.

even he is even tankier.

I think in general he has more than 1 counter... but also he is easily kitable. Any champ that gets fed will dominate. If he FB you then just cs at tower. No need to give him more kills. Obviously if you are complaining because he is diving you after he killed you 2-3 times, then that's your own fault. Try giving akali 2 kills early on.