Disable auto-pairing of characters in Textmate 2?

You can disable it for a given bundle as explained in this issue on GitHub. Basically you have to edit an option file of the bundle and add smartTypingPairs = ( ); near the end of the file.

I don't know if this can be generalized using the .tm_properties files but you are welcome to try (and report your results).

There is also a user defaults key for this:

defaults write com.macromates.TextMate disableTypingPairs -bool YES

Automatic "Typing Pairs" is a TextMate 2 Hidden Setting

When you type an opening brace, parenthesis, quote character, or similar, TextMate will insert the closing character.

Disable via Terminal:

defaults write com.macromates.TextMate disableTypingPairs YES