Loctite Red 271 - It takes a lot of heat to remove, 500+ F. Often, I use a wood burning pencil or soldering iron to apply very local heat.
Once, I used Epoxy on a very heavy recoiling dangerous game rifle. Those mounts and scope stayed on for many years until sold.
I have used fingernail polish on some screws, and a soaking in acetone helped in removal. However, some screws could be removed similar to Loctite Blue 242