I did a slight variation for the 5000 damage achievement, which may or may not be easier than the one listed above.
I used Jessica and Renova. Jessica needs 1 gauge, Renova needs 2 gauge. Combo starts with Jessica. The first j.C has to hit as a Counter. It is easy to create Counter situation by pressing LT (Taunt) on 2P before jumping.
22C j.CB 2A2B5B5C 236SP 2A2B5B5C D 5B5C 623SP 2C6C Meta 641236C 641236C
I had a lot of trouble doing dash cancel followed by 6A so my combo does not involve dashing at all. You just need to hit the correct direction and buttons at the right time. If done correctly with Counter hit starter, you should end up with 5027 damage which is just enough for this achievement.