Did you read my post ?

I clearly stated that you should be able to create a double-spending transaction (which won't be dropped by all nodes) if the RBF-tag is set.

nc50lc just mentioned that this should work if the RBF-tag is set in your original transaction and if you are using a compatible wallet to do so.
So, actually.. you should be indeed interested in RBF.


If you however want to double spend a transaction which does not have the RBF flag set, your OP wasn't clear at all..