You use a killer tool to remove an old printer driver. The tool deletes a shared .dll file that Windows Explorer relied on. Suddenly, your taskbar stops responding. You are now facing a Windows repair installation because of a "cleaning." The Verdict: Who needs a killer? The average user likely does not need a killer uninstaller. Windows 10 and 11, as well as modern macOS, handle orphaned files far better than their predecessors. Leaving a few hundred kilobytes of registry keys behind will not slow down an SSD-equipped computer built in the last five years.
A true "killer" uninstaller does not know the difference between a useless orphaned file and a shared system file. For example, a runtime library (like Visual C++ Redistributable) might appear to belong only to Game A. If a killer uninstaller removes it, but Game B also needs it, Game B will crash without warning. killer software uninstaller
If you are the type of user who enjoys digging into regedit and knows what a CLSID is, go ahead. For everyone else, trust the native tools. Those "ghost files" are usually just sleeping peacefully, doing no harm. Let them be. You use a killer tool to remove an old printer driver