A boy stabbed a student in the back after trying to steal his clothes.
The 16-year-old was with a group of mates involved in a string of offences in March, Bristol Crown Court heard.
In one incident the boy told a student he intended to take some of his clothes.
When the student walked off the boy stabbed him below his shoulder, puncturing his lung.
The boy, of no fixed address, pleaded guilty to wounding with intent to cause grievous bodily harm, posssessing a knife, robbery and assault.
Judge Timothy Rose sentenced him to 32 months' youth custody.
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He told the young defendant: "You went after him.
"You struck him in the back with a knife, you stabbed him.
"It was nothing other than sheer, mindless, gratuitous violence.
"You could have killed him.
"If you did kill him you could have been here on a murder charge."
An order was made to preserve the boy's anonymity.
Timothy Hills, prosecuting, said when youths in Cabot Circus hassled a female Deliveroo rider her husband, Christiano Pina, had a word with them.
As a result the boy punched him in the neck, the court heard, before the group ran off towards the city centre.
Later that day a group of youths surrounded three boys on mountain bikes, and hit one.
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The cyclists decided to abandon their bikes and run and the defendant picked up one cycle and advertised it for sale online.
Mr Hills told the court the next day a group of youths approached three 19-year-old students outside the Bank Tavern.
After the defendant declared he was taking certain clothes and shoes, student Evgeniy Turapov walked off and was stabbed.
Mr Hills said: "He felt an electric shock below his right shoulder.
"He saw a dark sleeve and a white hand striking him in his back.
"It was the defendant stabbing him in the back with a hook punch motion."
The court heard the students went back to their accommodation and called an ambulance and police.
Mr Turapov was taken to Southmead Hospital and was found to have sustained a deep wound which punctured a lung.
John Stokes, defending, said his client suffered from low self-esteem, negative self-identity and low emotional maturity.
He said: "This is highly likely to be the result of negative peer group influence, which has impacted on his educational progress.
"A report says he has a strong need to be accepted by peers."
Mr Stokes said his client had not been in trouble with police in the past.
He said the boy became involved with "others more sophisticated in criminality" and was pushed forward by them.
