Billy the 15-week-old kitten was found injured and starving in a Preston park on September 20.
His fur had been cut off and his testicles had also been severed.
He was taken to volunteers at Blackpool Cats in Care rescue, who rushed him to the Robert Jones Veterinary Surgery on St Annes Road, South Shore.
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He was later found to have suffered a shattered pelvis, and had nerve damage.
He was transferred to an orthopaedic vet in Liverpool, where vets advised volunteer Janet Moores to have the kitten put to sleep.
She contacted television’s ‘supervet’ Noel Fitzpatrick in the hope he would be able to save Billy’s life. However, he was unable to recover, and he was euthanised on Monday.
Janet said: “We are absolutely devastated. We have had thousands of messages from people from all over the world.
“We must have had 300 or 400 offers of homes for him. I have never known the whole of England stand up for a little kitten. Everybody has taken him into their hearts.
“Whoever has done this has to be brought to justice, because what are they going to do next? What they have done to a kitten is just barbaric.”
An RSPCA spokesman said: “We are continuing to investigate this case and, as enquiries are ongoing, we are unable to comment further at this stage.”
An online petition urging police to ‘find the perpetrator of this barbaric crime and prosecute them to the fullest extent of the law’ has been signed by more than 23,500 people.