Revo will work IF the app is still installed, i.e., shows up in UNINSTALL PROGRAMS. What Revo does is to launch the apps uninstaller first, then it scans the reg and directory tree for leftovers.
After the app's uninstaller runs, the app, NOT Revo, may return a <you have to restart> dialog or an error message of some sort: IGNORE THEM. (If you restart, you will terminate Revo before it completes its end of the uninstall; if you get an error message saying the uninstaller failed for whatever reason, Revo will finish the job).
After you close the restart/error dialog, Revo will take over and scan for leftovers. If the app uninstaller uninstalled nothing, then Revo will locate the reg entries, files, directories and give you the option to select/delete all of it. On occasion, when Revo is finished it may alert you to restart if it could not remove files or directories. Then, and only then, do you restart. By the way, when first launched, Revo gives you a choice between four different uninstall modes (how aggressive it is): I always select ADVANCED. If you are concerned that you might inadvertently delete needed shared files (I've never had that happen), create an image backup of your system before you proceed.
If the app does not show up in Revo, and you cannot reinstall/uninstall it, then remove it manually.
Monk