You have a binary process (yes/no, on/off, approve/delete) so you should use an element that allows for this behavior, such as radio or toggle switch . In your particular case, where you don't want 2 elements, but just one, I'd go with the switch.
An undetermined status would be very confusing unless you clearly label this and explain the user what to expect. One example of your behavior is Filezilla's Change File Attribute screen:
Here, you can have 3 states: unchecked, checked and "neutral" to keep the original permissions. But this is a really confusing way to do things and I'm providing it just as an example on how NOT to do it
Also, take a look to Checkbox vs toggle at UXSE for some additional information and concerns