Norse Mythology's Vanir were a race of fertility gods, who spent their days making the world flourish with plants and children... Oh, and they almost destroyed the Aesir.
Nymphs were usually kind and flirtatious, but piss one off and you're likely to be drowned and gutted. Or, saddled with a curse so horrible that you'll wish you were drowned and gutted.
Most people seem to think of Demeter as peaceful and calm, the goddess of the harvest and growth. One of the lesser known myths shows us just how awesome she can be: a King cut down her favorite tree. So she got one of her handmaidens to fetch Hunger, and sicced her on the King, until he ate everything in his city, spent and sold everything he had, even his own mother, and then ate himself.
Not to mention the whole "If I don't get my child back, I can and will kill everything on this planet" thing.
And then there's the prophesied Second Coming. The first time Jesus came, he was generally peaceful. The second time? Not so much. There's a reason he's called both the "Lamb of God" and the "Lion of Judah".
Many verses, especially Nahum 1:3, gives us the description that God is "slow to anger", but when evil strikes, He will stop at nothing to punish the evildoers.