Will {kalonian hydra} trigger with {domri rade} -2 ability?
Fighting is not attacking.
"When [name] attacks..." means, specifically, being declared as an attacking creature during the Declare Attack step.
So attack and double hydra counters then second main domri minus ability best option I guess
701.10a (http://imtgapp.com/forum/index.php?action=imtg;area=rule;number=701.10a): A spell or ability may instruct a creature to fight another creature or it may instruct two creatures to fight each other. Each of those creatures deals damage equal to its power to the other creature.
The hydra would just deal damage but not attack, so no trigger:)