CalendarMD has one sole purpose of existence: deleting events from google calendar in bulk, so I called it CalendarMD, where the MD stands for mass deleting. You search for the events in a specific calendar, and a list shows up. Scroll through the list to make sure you want to delete those events, and press delete.
I made a Free Android app with react-native. The code is on GitHub. Neither the style nor the code look not pretty, but it was the first app I made on React Native. Thinking back, this shouldn't have been a mobile app, and would have done better as a web app, because people are not going to install an app just to delete events from their calendar. I've since built another app for tracking the carbon footprint of food, Foodprint.