Oh yes, they can do enormous amounts of damage to vehicles, and they aren't all that safe to be around people, either! Tame ones which are accustomed to having people around can still have a show of temper and disembowel anyone who upsets them - the wild ones shouldn't be approached at all. Size doesn't matter. Although there are many roadkills, it's surprising how often the kangaroo comes off better than the vehicles! They are an absolute menace on country roads. They'll run along beside your vehicle for miles and miles, then without the slightest warning, they'll jump in front of your car and WHAM! One bruised roo, one written-off car. Emus are quite good at this game, too. I have never figured out why they swerve in front of the vehicle, never behind it.
As for those cute, cuddly little koalas... If one enters your garden, you lock up your pets and your kids, and immediately ring the local Koala Rescue, and soon somebody arrives armed with nets on long poles, and heavy gauntlets and other impressive protective gear. Those little darlings can rip a child or a dog to pieces in no time flat, and they do it, too - frequently. Never, never approach one in the wild, and don't upset a tame one, either!
How do I know? I spent much of my youth in the Outback, now living in Koala Territory. I'm just glad the Tough Guys are a thing of the past.