The Karma build for Support is Shurelya's Battlesong and Arcane Comet. This LoL Karma guide for Support at Platinum+ on 13.24 includes runes, items, skill order, and counters.
Karma Counters
51.0%
(+1.8%)
(-1.3%)
6.5%
(+0.5%)
1.5%
(-0.2%)
432
(-13)