Melee % isn't a stat like agi, vit, psy, str or int but afaik there is no limit beyond 100% on attack forces or dd.

The new upgrades have 70% Melee and or 70% Magic attack. They can combine in dual wield to 93% (70% main hand 23.3% off hand) melee.

You will find many of the end game upgrade users have actually wrapped (pos->neg->pos again) the melee or ranged attack force.