Out of most of godzilla's foes destroyah is malicious and takes pleasure from hurting his foes. Makes sense that he'd laugh after brutally beating another monster.
6:26, 6:30 - epic KO. Poor Godzilla. 14:45 - god helps Megalon, if he was hit such bone-shattering strike IRL. 16:32 - poorly Gigan has received such kick even without starting fight back. 18:23 - AGAIN!!!
Orga is much better at close combat due to having the biggest forelimbs from all monsters, enabling him to deal MASSIVE damage, but Destoroyah is WAY better at long range thanks to his oxygen destroyer energy absorption mines that'll throw opponents around whole battle arena like if they were ragdolls.