Thanks for the kind words!
As for the hydra ; I prefer ravenous hydra for a few reasons.
Titanic hydra is based around giving your basic attacks a slightly larger kick later on. Ravenous hydra gives you lifesteal unlike that silly juggernaut item, which actually is quite the big of a deal. The actives matter a lot too. With ravenous hydra you can throw yourself into the fray, get someone with your W and cancel it's animation with it's active. Also, ravenous hydra is waaay more effective when built first, because if you get fed and rush titanic hydra you are basically shooting yourself in the foot because this item doesn't provide nearly as much damage as it's ravenous component. If you think of titanic hydra later, in theory, it's better, because it gives your autoattacks slightly more damage and also the health, but at that point, you realise that it's active is still worse. Titanic hydra is less of a bursty item, which is the reason why i prefer ravenous hydra on renekton, a champion that is for the most part centered around his burst.
Oh, also, the additional damage you get when ulting is rather insignificant. It gives you +2/4/8 damage for your basic attacks at best.
I highly apologize for the late reply.

Hey
Its a really nice guide.
But i have one question. Why do you prefer Ravenous Hydra and not Titac Hydra? Since Renekton is tanky as hell.
R gives also a dmg boost.

Yes, empowered will still deal the 3 procs and full damage, but with the slight "buff" to Renekton, you can cancel it even quicker.

Does Renekton's w still deal full damage and proc black cleaver stacks if u cancel it with tiamat/hydra?

Thanks for the guide, it really helped me a lot when starting to play with Renek. After 3 days of only playing him and following your guide I manage to go out nearly every game positive and helping my team a lot. A big thank you. :)

I will add Tryndamere to the matchup section.

Thanks for the guide, but i have one question. What about Tryndamere? I seem to be struggling against him, if he builds crit straight up, it's impossible for you to handle him.

Yeah,it is messed up.It really is...

I've done some changes.The Pros / Cons section is now less weird in terms of coding.Also,i have mentioned Tiamat in the item section.Thank you for reminding me,i really forgot to say it.

Tiamat is also an item worth rushing in some cases, you could mention it.

Your coding in the "Pros and Cons" section is a bit messed up. Check whether you've always used a cloding bracket /] when needed and/ or take a look at this (again).