I'm afraid you've almost certainly bent your battery beyond recovery. Reverse-charging lead-acid cells will depolarise them, then attempt to repolarise them the other way around, which is very unlikely to have a happy outcome. An attempt at redepolarising and rerepolarising won't end well

You might get lucky, as lead-acid cells are actually pretty robust, but I doubt it. Even if it doesn't go pop in the process, it will definitely and dramatically affect it's longevity, and not in a good way.

pca