If you want to take out Frank along with the others, you will need to sabotage his fireworks in Deathloop. You'll need to access a cargo container in Karl's Bay, which is locked with a code that only Otto knows. There's a few moving parts to manage here, which is why we've put together this walkthrough on sabotaging Frank's fireworks and killing him in the evening.
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Deathloop: How to Sabotage Frank's Fireworks
To sabotage Frank's fireworks, you will need to travel to Updaam in the morning. Otto's workshop will be open during this time. It's found near the entrance to the library. It will burn down at Noon, so make sure you visit before this. Go inside and note the machine that is running loudly in the corner. There are cables running from it that lead to generators. Destroy each one to disable the machine. Return in at Noon to read Otto's computer files and gain Frank's security code.
Now you will be able to sabotage Frank's fireworks. Head to Karl's bay and look for a storage container at the back of Hanger 1, in between the alley that joins the two hangers. Open the container and you will see a console to tamper with.
This is the most important part, as you will need to select the correct option from a list of available weakpoints. Choose 'Jam rain flaps'. This will ensure that the fireworks explode prematurely later on. You can now continue through your loop. Frank will die automatically during the evening section in Updaam.