For an instance I believe if that thief should get caught, he should have his hand that held the knife cut off or at least a finger or two. Don't bother wasting tax payers money on sending him to jail. Likewise swift and appropriate actions for other deeds such as car vandalism. I'm in agreement with the caning they do in Singapore.
I agree that jail (i.e. taxpayer-funded room and board) is a complete waste of money the way it works now. Jail sentences of many years or even decades are pointless. Incarceration should be used to reform a person, if indeed they can be reformed, not as punishment. Such reform programs should be modeled after China's highly successful reform through manual labor program (a combination of rote labor plus "reprogramming" ). At most this reform would take a few years. In most cases my guess is weeks will do. Once deemed reformed, the person should be let back into society. If they commit another serious crime, perhaps they get one more try at reform. After that they get sent off to some island or other fenced off space for unreformable convicts. There would be no cells, no guards, no public support. It would basically be a place where inmates will survive or die by their own hands.
For lesser offenses caning and other forms of corporal punishment/public humiliation are very appropriate, especially for juvenile offenders who would be punished right in front of their fellow gang members. I'm not on board for cutting off body parts. By physically disabling a person, you decrease their ability to earn an honest living. I couldn't do what I do if I was missing a hand, for example.
What would be the downside of such stringent punishment? I guess the deeper question is, would it create a deter to crime.
IMHO the only downside would be the complaints from people who see such a program as "inhumane". Well, keeping people in jail for 50 years is probably even more inhumane, and it hasn't done much to deter future criminals. At least under the program described, the vast majority of petty criminals will have their "careers" nipped in the bud, and nobody will be spending their natural lives behind bars.
The deeper question of not having people turn to crime in the first place involves raising our children to higher standards, providing more economic opportunities, and taking many petty laws off the books. It's one thing to have laws against murder or rape or robbery, quite another to criminalize many things which aren't necessarily harmful to others. Our drug laws are a great example. Provided you're an adult, you should be free to use any substance you want no matter it's effects on you. If you happen to commit real crimes while high on something, then there are laws to deal with that already.
Sure, this is a highly complex issue, but crime can be dealt with better. There have been societies in the past where murder and robbery was practically unknown. Maybe we should look at what they did. I suspect most of the reason was how they brought up their children. Today's society glamorizes violence in movies and covets wealth. Both things lead to antisocial behavoir, even among law-abiding citizens. In a society where someone's standing was based more on their knowledge and usefulness, rather than their net worth, there would be a lot less crime. Maybe a good start might just be stressing cooperation instead of competition in schools.