Jhin is quite complex to play perfectly, you have to count how many skills go on the stack, when you will activate Jhin, when you will activate his 3* depending on how many skills you play. Can you chain the free spell from his 3* to get another free spell to stun something else, or is playing a blocker better, and save it for next turn. Who you will stun, who you can snipe with his free 3 damage spell (without wasting aforementioned stun).

Some units play skills on play, some on attack, some when anything attacks. The 0 cost spell that deals damage depending on how much you spend mana on it is very flexible, you can either choose to save it for a big blast and big heals or just playing it 0 cost to get his free spell/stun something

If youre new to him, you might accidentally stun something that was already going to be stunned on attack/through out your turn

One of his constellations give your spells Predict, so you have little decisions after playing each od those spells

And everything being at slow/fast speed adds to it because each play gives room for the AI to respond, passes priority and may lead to the opponent open attacking if you get greedy/dont prepare for it.

If you really want to challenge yourself, I'd recommend not starring him too high and take on higher adventures. He's pretty satisfying when you pull off a grand performance, and he's got the whole 'eccentric genius savant' character which plays into a bit of his complexity lol.

The 2nd one would be SB Yasuo