No Dark Side GL can efficiently counter a JMK/CAT/GK/GAS squad.

I have done some more testing. The LV squad do counter JMK, but very poorly. The banners in GAC will be terrible. LV will be going on defence in GAC.

In regards to arena, there are still some high relic JMK squads that are problematic. A lot of the battles in arena I have done, LV is only scraping through by the skin of his teeth.

JMK is the better GL. LV requirements with 4 relic 8’s, and 4 relic 7’s is considerably more then JMK’s.
The amount of money needed to unlock LV, is considerably more in return for an inferior GL.