If you have good reactions, any time Arjun does Arm of Justice, you can DI the followup on reaction. Just keep an eye on his back and if you ever see him turn around and show his chest, hit DI. You don’t have to guess. This works even if you are hit by the first part of Arm of Justice and it’s not a Counter Hit, because the second half never combos on Hit normally (except for the HP version, which launches you on the first hit). I have bad reactions and I can do it consistently in Training Mode (in a real match I’m super spotty because my reactions are really bad). If you have any sort of decent reactions, it’s a very big tell seeing him turn around. Just keep a lookout for his chest. LOL!