Amumu

Amumu is really strong against Rengar, because he builds a lot of armor and has 2 stuns. He is strong in dueling and teamfights. Use Conqueror and get Red Smite. Try to kill him when he doesn't have ult. Build Lord Dominik's Regards.

Dr. Mundo

Mundo is really strong as he has so much health and still does a lot of damage. Go for Conqueror and Red Smite. Try to kill him when he doesn't have ult. You will need to build Mortal Reminder after the mythic and have someone with you to kill him.

Ekko

Ekko can be an assassin and a bruiser, which makes him strong, but the only problem with him is his ult. Go for Conqueror and Red Smite. You should be able to kill him when he doesn't have his ult.

Evelynn

This is mostly a skill matchup as if she gets lvl 6, she is really strong. The way to counter her is to go for Electrocute and get Ultimate Hunter. Try to make her fall down early, since her powerspike is at lvl 6. If you don't manage to kill her before she hits lvl 6, your only option is to ult in a teamfight and try to kill her.

Fiddlesticks

Fiddlesticks is almost always weak, the biggest problem being his healing, ult and vision. Go Electrocute and get Blue Smite. He can escape your burst with his flee, so try to smite him to slow him. He has vision, so if you find one of his wards get out of there, as probably his team will come. His ult is really strong for teamfights, so just fight when he's not there or wait for him to waste his ult. If he doesn't do any of those, try to ult him when he's alone.

Gragas

Gragas has damage and is tanky. Go for Conqueror and get Red Smite. You should be able to kill him early.

Graves

Graves is a difficult champion, so look if he messes up and punish him. Go for Conqueror and get Red Smite. Wait for him to use his smoke, as it will not allow you to leap and then you should be able to kill him.

Hecarim

He is tanky, has a lot of damage and a lot of mobilty. He is a nightmare. Go for Conqueror and Red Smite. Try to kill him early. Like Evelynn, if he gets ahead, there is almost nothing you can do about him.

Ivern

You counter Ivern, since when he places a bush, you can leap from it. He is nothing without his ult and his team. If he's alone, try to kill him, shouldn't be that much trouble. The only problem with dueling him is his root and his ult, which can knock you up. But you can kill him easily early.

Jarvan IV

Jarvan is a tank and does a lot of damage. Go for Conqueror and Red Smite. Try to kill him early. If he has lvl 6, you should win the 1v1 if you ult him, but be careful if he ults, because you can't go in bushes.

Jax

Jax counters most of the champions in the game. Go for Conqueror and Red Smite and try to kill him only if you are ahead by a lot. Jax can catch up to you easily with his Q, has a lot of damage with his W and counters all of your damage with his E. Try to make him waste his E. If he does, you need to waste his R too, because it makes him a tank, even he builds only damage. After that you should be able to kill him.

Karthus

Karthus is a mage and can kill you easily if you don't dodge his Q's. Go for Electrocute and Blue Smite. You should always be able to 1v1 him. Watch out for his Q's when he's dead. If you're low he will just press R and you're dead.

Kayn

Kayn is weak before he has his form so try to kill him early. Go for Conqueror and get Red Smite. If he goes for Shadow Assassin, he will one shot you Try to dodge his W or to one shot him first. If he goes for Darkin, try to kill him with your team and smite him.

Kha'Zix

This is a very interesting skill matchup. You can't 1v1 him when you're isolated, otherwise you should be able to kill him easily. When you both get lvl 16, try to kill him first and always stay with your team to not be isolated and avoid him one shotting you.

Lee Sin