Sprocket touching the biggest cog no matter B screw...how do I fix? My Shimano rear derailleur was destroyed, for some reason got into the rear wheel, so I had to buy a new one. Hanger was a little misaligned but I think I fixed it. 

I bought the new derailleur, changed cable and housing, the chain was pretty new.

All installed, checked L and H, and I noticed the derailleur was a little close to the cogs. but worked fine in all the 6 smaller cogs. 

When I try to go into the biggest cog, no matter the B screw, the sprocket is touching the cogs (with the chain in between) making a weird noise and sometimes it cannot even get up there.

The first derailleur was a Shimano TY500 6-7 speed. I ordered another one, a Shimano Tourney RD-TY300 6/7-Speed  but is doing the same thing!

The rear cassette has a biggest cog of 34T

I'm running out of options... only I can think is replacing the hanger to see if that is the issue.
Both the TY-300 and TY-500 are rated for a large/low sprocket of 28T to 34T so they are both within spec.   There are no other variants, only the -SGS long cage is available.

https://bike.shimano.com/en-EU/product/component/tourney/RD-TY300-SGS.html

https://bike.shimano.com/en-AU/product/component/tourney/RD-TY500-SGS.html



I'd strongly suggest checking the the hanger alignment before spending more money on replacement parts.

You need a bolt that fits the hanger (possibly salvage this from your old destroyed unit) and a longish flat rigid bar, and something to measure down to the rim.



The measurement of the offset to the rim needs to be as accurate as you can, but within 10mm at the rim should be adequate.



The other option is that your B screw is damaged, bent, not pushing hard enough, or the stop is broken/damaged/missing.  A clear and well-lit photo of your frame and hanger would help show if this is the problem.