For getting this secret achievement, you have to perform a combo with a total of 5000 damage or above AND defeat your opponent afterwards. This means you can do it only in Arcade, Online or Versus (which is recommended) because your opponent can´t be defeated in Training Mode.
There´re a buttload of videos on youtube but most of them come without the correct notations. I´ ll post the 2 examples I´ve used for getting the achievement. The basic idea is to optimize Eva´s Berserker ability, which adds 40 percent more damage to all of your attacks after switching your characters and during your action in the Meta World.
IMPORTANT: the selected videos are from the PC Version of Ougon Musou Kyoku X and also work with the console version of Golden Fantasia X (currently running version 1.01). It´s really important to note that some of the other combos shown on Youtube do not work in the console version anymore (Lucifer´s 3C loop for example, or the 5K Combos for every single character). Both of the examples do work but I just wanted to bring it up here since I´ve been reminded to state it.
The first example uses Eva-Beatrice´s C-Pudding to land another j.C from Jessica which inflicts A LOT of damage together with Eva´s ability.
Default setting:
Controller - ingame notation
X - A
Y - D
B - C
A - B
LB - Meta World (A+B+C)
LT - Taunt
RB - SP (Special, or A+B)
RT - Throw (B+C)
Example 1 (all notations are used for the default setting):
Eva: 22C D
Jessica: 22C j.CB 5A5B2B5C Meta (A+B+C/LB)
j.CB 5A5B2B5C 3C 214C 623A+B/RB 6C 641236C Stun
22C j.CB 2A2B5B5C 236A+B/RB 5A5B2B5C Dash Cancel
5A5B2B5C Meta Dash 2A2B 3C 6C 641236C
Example 2:
Eva: D
Jessica: 22C j.CB 2A2B5B5C Meta Dash
5A5B2B5C 3C 214C 236A+B/RB 6C 641236C Stun
22C j.CB 2A2B5B5C Dash Cancel 5A5B2B5C 236A+B/RB
2A2B 3C 6C Meta 641236C
Meta Dash means you have to activate Meta and then tapp 66 quickly to perform a dash to reach your opponent. Dash Canceling will deplete your full Partner Gauge and is performed by tapping 66 after you landed a hit.
If you´re having trouble with the two examples, you can try the combo I used for this achievement:
Eva: D
Jessica: 22C j.CB 2A2A5B5C Meta Dash
5A5B2B5C 3C 214C 236A+B/RB 6C 641236C Stun
22C j.CB 2A2A5B5C Dash Cancel 5A5B2B5C 236A+B/RB
2B5B5C C.... (press C rapidly)
I lost some damage due to the second 2A after each j.C but the mashing C part at the end made it far more easy for me (and you only have to activate Meta once). Even if you´re missing a hit here and there, it will net you 5050+ damage as long as you´re around 36+ hits at the end.
If there´re any other questions, feel free to drop me a message.
Many thanks for reading!