I agree that this is a blindpick guide. not for ranked. BUT it does exceedingly well (for me atleast) in blind. It is true that ap, mana and AS are fairly useless on renekton. But just because one attribute doesnt work doesnt mean one should ignore the others. Trinity force grants massive damage whenever renek uses a spell, whether dash or stun or whatever. And the AD, HP and movement speed just sweetens the pie. Sure madreds gives AS which is not very usefull. But the damage and armor which are easily forgotten are excellent for renekton. there are 3 items in the game that gives both.
So i agree, it's for blindpick, but it's very good in blindpick, and it slaughters the enemies carries. Thats the core of the build, culling the meek. If you need a tank, dont take this build. but if you have a jungle mao kai and a support alistair you wont need more tankiness. Then you send this fella solotop.

Things to consider.
AP benefits Renekton so little you might as well not even get it. The mana and AP in trinity force do nothing for him, and as for the madreds, Renekton is not an attack speed champ. The items you selected were horrible and should not be used in a top lane Renekton

One thing i did like were your runes. They were tanky, but i feel there is not enough damage output, and because of Renektons strong early game, i feel the more damage the better. I did also like the leveling of the abilities, although your Q and E could be switched depending on the matchup.

Overall, Guide needs LOTS of work and remake. I feel this is not viable whatsoever for anything past blindpick.

There's so many wrong things on this guide i can't even list them all

Nerf plox

it's so awesome it really fits my play stile! i have to recommend this to an agressive player renekton