Tartar
bear
bellyacher
complainant
complainer
crab
crank
croaker
crosspatch
dragon
faultfinder
feist
fire-eater
frondeur
fury
griper
grizzly bear
grouch
grouser
growler
grumbler
hothead
hotspur
kicker
kvetch
malcontent
murmurer
mutterer
querulous person
reactionary
reactionist
rebel
sourpuss
ugly customer
whiner
absconder
backslider
dodger
evader
poltroon
straggler