In a climbing bike, I would look for:

-Lower weight, especially in the wheels. Overall heavy bike is OK, but lighter uppers (seatpost, saddle, stem, and bars) help when rocking. Lighter wheels help acceleration.

-steeper seat angle for easier transition from out of saddle to seated

-stiff bottom bracket for full power transfer

-short chainstays.

-crankset with low tooth count (24 min) and a close ratio cassette (28t max) for many usable low gears with small jumps in between. 32t are nice but the jumps are too high between gears. I like to run the smallest chainring possible for the BCD and no larger than 28 or 30 in rear. This also allows for a short cage derailleur and snappier shifting

-lower front end than high

-wider bars than narrow to allow breathing

-maybe bar ends for leverage