I know my ball cap is too small to read in my avatar on here
It says "once a Marine, always a Marine"
That is why I make so many dumb Jarhead jokes
but, on this topic, all kidding aside,,,,,,I have actually broken paint bottles trying to get them open,,,,,and even cut the "holding hand" once, while prying the cap off with pliers
Now, in my old dotterage,,,,,,,,,if a cap is that stuck,,,,,,that paint is probably as old as my son, lol (he was born in '79, the year I got out of the Corps)
So,,,,,I just don't play with it if it wants to be that stuck,,,,,,I use it for "shooting a basket" into the ole round file,,,,,,and either pull out another bottle with a newer date on the office dot I put on top of them all,,,,,,,,or get a new one soon at the paint store
as expensive as hobby paint is,,,,,,,it reallllllllllly stings if you get that paint carrier fluid in a fresh glass cut on your hand