Trying to brute force the 777 Damage for the Lucky Achievement instead of hoping to get it randomly, there was a consistent method I found using some math and testing with different characters and combinations of equipment/karma.
Should be noted that this was done right off the bat after leaving the city. (With random exploration, no real mainquest progress)
Stats and Character Setup

So the goal is to hit 247 attack stats so Theresia’s Sprint Attack deals exactly, and consistently 777 damage to the level 10 Orges near the starting area (After you leave the castle go right and head past the broken goddess statue taking the lower road)I’m not certain her level mattered as much as the attack stat but the following setup gave me 777 damage consistently against these targets. If you are unsure and want to be certain I had her at level 9 when I found the right setup.

In my case, my base stats at level 9 were 116 attack and with karma/equipment I pushed to 247.

Leveling up this Karma got me 119 Attack, depending on your setup the Karma’s may vary, the real RNG comes from what equipment you are able to make.

Here I had gloves that gave +12 attack. I also had items that had higher attack values but the main goal is to just achieve 247 through any combo of stats with equipment and karma. Get whatever setup you can manage and aim for that 247 marker.
Afterwards, all I did was sprint at the Orges and performed a single attack unlocking the achievement. Hopefully this helps other people get this easier then randomly stumbling on the setup with other attacks.
Summary for the setup I used:
– Theresia Level 9
– Sprint Attack
– 116 Base Attack
– 131 Attack from Karma/Equipment
Full Video Recap of all the information above with all stat menus in case I missed something: