The first effect of “King Dragun” is a Continuous Effect. The second effect of “King Dragun” is an Ignition Effect.
Your opponent cannot target a Dragon-Type Fusion Monster with “De-Fusion” while “King Dragun” or “Lord of D.” is on the field because “De-Fusion” targets.
“Divine Wrath” is NOT a card that targets, so “Divine Wrath” may be used against Dragon-Type monsters while “King Dragun” or “Lord of D.” is on the field.
You can chain “Divine Wrath” to the effect of “King Dragun” that Special summons a Dragon-Type monster.