To chop a dog's tail bit by bit

To 'rip off the band-aid' is the best I can come up with. A band-aid that is removed slowly will hurt more than one that is ripped off forcefully, and the idiom has the connotation of doing something painful decisively.

https://idioms.thefreedictionary.com/rip+the+band-aid+off

rip the band-aid off
To do something painful or unpleasant very quickly so that the discomfort, while typically more intense, is short-lived. "Band-Aid" is a brand of adhesive bandages, so it is sometimes capitalized in this usage.
You just need to rip the Band-Aid off and tell them the bad news.
I tend to obsess about things if I don't take decisive action, so I try to rip the band-aid off whenever I can.