I'm practicing my parrying and notice, in PvP, that it's harder to parry the heavier weapons when wielded in two hands. Especially Ultra Greatswords and Maces I haven't yet been able to parry in PvP. Maybe I need to continue working on my timing, but it made me wonder:
Dark Souls 3 PvP: Is it possible to parry all melee attacks?
If not, which are the known melee weapons (or ways of attacking) that inhibit the opponent's option to parry?