Iris stopped their pokemon from battling each other the first time, and both Clair and Iris have calmed an enraged Druddigon down by showing it love and care.
It's nice to see that Charizard has learned to use its strength when it is necessary instead of attacking anything that it sees. It's not that Charizard is weaker than the Dragonite, but it has compromised itself to settle its conflict without battling them. Charizard was sent out to help the Dragonite remove the steel door, and it followed Ash's command to let the Dragonite duo handle it. The mission to find the shiny Druddigon was more important.