I've had an enemy xin in alot of games in the past and late game he'd just go into our full time and kill everyone. I'm really at a lose of words on this kit being seemingly broken with a knock up, life steal, and knock back. Is there a build or item I should rush against him so I'd win fights against him?
He isn't that Overpowered in the current meta. Every champion may seem Op when they are fed to the point where the do Damage & have insane amount of survivability. However, if you want my advice in countering Xin Zhao, you should look for a champion with high damage output with escapes. Like Ezreal, Tristana, etc. Since Xin Zhao only has one form of attachment, which is his E, meaning he will be extreamly easy to deal with the moment you Tristana W, or Ezreal E away, unless he has a blade of the Ruined King, which would make him very squishy, and easy to kill off. Other than champions that does high damage outputs, you can try too look for champions with insane amount of CC / Lockdowns, like Maokai, and Malphite. Maokai would just constantly be locking down XinZhao, and give your entire team % Damage Resistance. Malphite's E will make Xin Zhao literally useless during team fights. The only Items I can think off that will help against Xin Zhao, are:
"Frozen Heart" - Gives Armor + -20% atk speed, which is not good against attack speed oriented champions. "Face of the Mountain" - Gives Health to your allies, allowing them to be tankier "Zeke's Herald" - Gives insane amount of damage output to both Ap and Ad
Any damage oriented items would help kill off champions, but it depends on what champion you are playing. The last thing I would offer is taking summoner "Exhaust" with you, which can make any high damaging champions, useless for just a moment.
You don't his name is Win Nao for a reason.
Frozen heart isn't a bad item against him. Thornmail won't kill him but it would mitigate his 3 hit heal.
As far as counter picking him with champions a combination of slows and displacements tend to give him a rough time. Nasus' wither tends to ruin Xin's day. There's also Tristana and Alistar to instantly peel him off and remove his presence. If you actually want to kill him Vayne can do the job with her invisibility and self peel mixed with her true damage silver bolts. Lissandra also has a sweet ultimate to take him out of the fight as does Malzahar. There's also the route of always staying more mobile than Xin as well but in team fights sometimes you just cannot do that.
