I think canonically the most physically powerful race would be the Tauren and the most powerful class would be the DK (and no it isn’t because I post on one). We’re just talking raw strength. Most savage would definitely go more towards an orc (who also would be up there on raw strength).
Brains always tend to trump brawn though so a mage or even a crafty elf hunter/rogue would actually be the most deadly (someone proficient with traps and controlling the battle before the battle even starts). Same reason why Batman is considered to be the most dangerous adversary anyone could face since by the time you seen him, you’ve already played right into his strategy.