Even gods can be bratty. Loki has basically been nursing the age-old "my brother is more popular than me" grudge, and his overreaction is apocalyptic. His jealous need to prove himself and edge Thor out carries across not one but two films, leaving the destruction of a small New Mexico town, then New York City, in his wake. How embarrassing must it have been for Thor to tell the other Avengers that they're all caught up in this mess because his half-brother is a self-conscious brat?