Mama Grizzlies

(HT: Telegraph.co.uk)

Seriously, you don't want to mess with mama grizzlies, or any mama bears in general.

"Then he went up from there to Bethel; and as he was going up the road, some youths came from the city and mocked him, and said to him, 'Go up, you baldhead! Go up, you baldhead!'
So he turned around and looked at them, and pronounced a curse on them in the name of the LORD. And two female bears came out of the woods and mauled forty-two of the youths." (2 Kings 2:23-24 NKJV)

And you don't want to mess with their cubs either, especially when David and God Himself were compared to mama bears.

"You know your father and his men; they are fighters, and as fierce as a wild bear robbed of her cubs. Besides, your father is an experienced fighter; he will not spend the night with the troops." (2 Samuel 17:8 NIV)

"Like a bear robbed of her cubs, I will attack them and rip them open. Like a lion I will devour them; a wild animal will tear them apart." (Hosea 13:8 NIV)

That being said,

"Better to meet a bear robbed of her cubs than a fool in his folly." (Proverbs 17:12 NIV)