I used to babysit a boy of 5 years old who would poop and pee wherever he wanted.
He wasn't actually allowed to do so but his parents had given up on potty training him.
He was not potty trained and his parents had kept him in diapers because he would not poop or pee anywhere but on the floor, diaper or anywhere else.
I finally though got him potty trained after 7 years old.
I decided to put him back in diapers at my house as well for a few months when I was babysitting him and then try later.
Then finally after he turned 7 I got tired of it and stopped diapering him anymore and made him clean up his own poop and pee.
He finally decided that it was better to use the toilet instead of having to clean up his poop and pee.
I also spanked him when he pooped or peed on the floor on purpose and he hated that.