Someone or something with an unusually large amount of strength is a goliath. Your soccer team might be nervous if you show up to a game and the other team's players are a bunch of goliaths.
This adjective comes from the Biblical figure Goliath, who despite his greater size and strength was defeated by the young David. So while it's fine to use goliath to simply mean "giant" or "strong person," it's even more fitting for something supposedly strong and unbeatable that's actually vulnerable. You might challenge a goliath of a developer that's threatening to cut down the oldest maple tree in town — and, like David, you just might win.