I already reported this issue long time ago...  I do play Total War Attila in Steam and I would like to know if I can finally get a solution to it.

These four (4) achievements are unable to get unlocked...  I even tried to re-play several times and with different factions not once but several times, but they are still not shown as completed or achieved or unlocked.  

These 4 achievements are :_

1.- Tactical Genius (Use 3 abilities using a single campaign battle)

2.- Show No Mercy! (Kill at least 1.000 enemy troops in a single campaign battle)

3.- Veni, Vedi, Vici! (Complete Grand Campaign by fighting and winning every battle)

4.- Caesar Reborn (Complete Grand Campaign on legendary difficulty by fighting and winning every battle)

It is really annoying that nobody answers my request for a fix. 

But these four are actually unlockable. There are other five like achievements that cannot be unlocked.

I dont believe they are bugged. They are just not very clear on the requirments.

I just completed Veni, Vedi, Vici! and Caesar Reborn. For both of these its not a simple victory. You have to acheive a Divine Triumph to activate both of these achievements. This was very difficult, particularly the requirement to destroy 40 other civilizations. Considering there are only 56 factions in total. For the last couple, I had to spark rebellions in a region and help them capture settlements before I could take them out. I have read other places that autoresolve is actually allowed for these achievements, however I did not use this at all, so I cannot confirm this. 

I have read other places that for the Show No Mercy!  achievement, you actually have to kill 10,000 troops in a single battle. This one I am a little confused about. Considering the avg unit size is 120, 20 max for each army, a 4 armies max per player, this would only be 9,600 troops, even while killing every single unit. 

I have also achieved tactical genius long ago. I would assume its probably multiple different abilities, and not the same ability multiple times. Either a general with many abilities, or multiple generals with different abilities. I dont remember exactly, but I can confirm it is not bugged.