I find this glitches I double and triple check to see if I have all the pyromancies and I do have them all. I'm not sure why it's not giving me the achievement
I believe that sometimes you won't get the achievements if you are playing offline. It happened to me before for some of my other achievements. Maybe try getting rid of one of your pyromancies and buy another one back?
There are 16 offensive pyromancies (13 if we exclude mist ones). There are then 4 support pyromancies (7 if we include mist ones). Then there's a total of 20 pyromancies, 19 if we exclude the one from the DLC.
They are really good, in general, quite sad with how they nerfed magic in Dark Souls 3
What? lol. Pyromancies in DS3 are OP af and essentially all of these spells are there, plus a few more. Plus rapport is super broken in that in affects almost every enemy, not just undead
Pyromancy was dumb in DS1. Any build with spell slots could use it, it doesn't have a stat requirement. It's not that DS3 nerfed it, it just properly implemented it as is own type of build.