Shimano's Deore XT Rear Derailleur handles the pressure! Its low-normal design moves the chain to the easy-pedaling gears (large cogs) with very little shift-lever pressure so it's easy to shift while climbing. Plus, the wide pivot design increases rigidity and longevity for miles and miles of crisp shifts. This combination of efficiency and light weight have long made the XT a favorite of racers and freeriders alike.
Largest cog this derailleur can handle: 34 tooth
Weight: 225 grams
Low Normal means that the derailleur spring assists shifts to the larger cassette cogs, which speeds and smoothes shifts and greatly reduces the chances of damaging the derailleur during upshifts because you can't force it with the shift levers.