As a Renekton main, I will talk to you about my favorite reptile on the Rift going from point to point on your topic.
But 1st, lets talk his passive.
Renekton is one of those champions that suffers when zoned. If he can't hit things, he can't stack his passive, if he can't stack his passive then he can't fight you. Now onto the rest of your points.
Auto attack enhancing w that stuns, applies on hit affects
Don't forget that it's also an auto-attack reset. During the stun animation though, unless you have a Tiamat variant, Renekton is locked into the animation, reducing your stun duration in 1v1s by the duration of his self-lock. The on-hit effects part doesn't matter in most cases unless he's doing the on-hit Renekton build or has a Tiamat variant (which will proct each Tiamat hit on-W slashes).
an armor shred 2 dashes e ability
The armor shred only occurs on the 2nd Dash if it is empowered by your passive, which he needs to hit the 1st to even use the 2nd. Good Renekton players don't even bother with trying to use the armor shred because the damage/healing from Q and the extra stun duration on W are far more valuable, making the armor shred a non-issues unless you're vs a noob Renekton or he has to proc it for the gap close.
a Q that heals him for a shit ton once it's empowered
Renekton's Q is a double-edged sword. Yes you can heal up all the damage you get delt, but you're also pushing the wave when you use it which is not what you want to do as Renekton. As Renekton you want to freeze the wave to keep your opponent zoned as long as possible so you get ahead easier while also stacking your passive off the minion wave (like I said before, if Renekton can't stack he can't do anything). To counter this, if a Renekton walks at you with the intent to tag you or push you away, walk into your minions. They won't aggro onto him because it's an AOE ability, but it will force him to push the wave to your tower where you can setup a freeze which denies him both minions and the ability to stack his passive. If he sticks around near your tower he becomes an easy gank.
and an ultimate that instantly grants him 300 HP level one
1st off it's 250-500-750 to correct you on the values. The health isn't even the problem when fighting an ulted Renekton though, it's that he generates his passive over time. You will see some Renektons sit in a bush and just pop their ultimate, staying there for a few seconds to generate enough fury for an empowered ability before even going in (which is a smart tactic to bait the enemy laner into thinking they're safe). Renekton can and will only dive you if you are low enough on HP. In most cases, it might be best to just leave lane if he has his ult available so he doesn't get a kill onto you.
To beat Renekton in lane, you need to not use a fighter champion.
You need a hard CC champion, a champion with high mobility, or a champion with good poke that has a little mobility.
Here are a list of champions I believe Renekton has problems with :
(Kayle at level 6) 
I picked these champions through experience of many matches with and against my lizard buddy.
If you want, I can go into detail as to why each champion I listed is a problem for Renekton.
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