I've only got a M badge in one tier X (my excuse is that I don't play tier X a lot lol), that was in my M48 Patton.
Requirements for that were -
3 detected
4 kills
3587 damage
11 pens
1340 blocked
5077 assisted
I think it must have been the assisted damage that clinched it.
In Garage: Red = Elite Blue = Premium
Light Tanks - NC-31, Pz 38H 735 (f), Pz II Ausf D, T7 Combat Car, T1E6-X, T1E6-X1, Locust, Stuart I-IV, Luchs, Chaffee, AMXELC, 59-16, T37, Snakebite, MT-25, AMX Chaffee, WZ-131, AMX 13 75, Bulldog, Lycan, Dragon Type 62, AMX 13 90, RU 251
Medium Tanks - Pz IV Ausf H, Chi-Nu Kai, Ram II, Pz V/IV, Skoda T 24, T-34, 25TP, M4A2E4 Sherman, Sherman III, Pz II/IV, VK 30.02 (M), Firefly, Boilermaker, Cromwell, Knight, Cromwell B, M4A3E8 Sherman, Fury, 40TP, T-34-85, Rudy, T-34-88, Comet, Panther, Champion, Krafts Panther, T23E3, Chi-Ri, T-43, Bigtop, T44, STA1, STA-2, M4A1 Revalorisé, Pershing, Centurion Mk 1, T26E4, Type 59, AMX CDC, Centennial, Atomic, Motherland, FV4202 (P), Vengeance T25, T67, M46 Patton, AMX 30, Leopard PTA, T-54, Centurion 7/1, Centurion AX, M48 Patton, Leopard 1, T-62A, AMX 30 B
Heavy Tanks - Pz.Kpfw. B2 740 (f), Excelsior, Churchill III, Captured KV-1, KV-1, ARL 44, KV-2, O-I, British Bulldog, O-Ni, Churchill VII, T29, Tiger (P), IS, Tiger 1, 45TP, Tiger I Hammer, Tiger 131, IS-2, Minuteman, Tiger II, King Tiger, Captured King Tiger, VK 100.01 (P), T32, AMX 50 100, IS 3, Fatherland, KV5, The Nameless, HMH AMX M4 mle. 49, T34, Caernarvon, 53TP, E-75, T-10, Mäuschen, Conqueror, 50TP, M103, T110E5, E100, Chieftain, IS7, Maus, T57, Super Conqueror, Object 277
Tank Destroyers - Pz Sfl IVc, The Hidden, Hellcat, T25/2, Jagdpanther, SU-122-44, E25, T28 Concept, Ferdinand, Borsig, ISU-152, AT15, Jagdtiger 88, Tortoise, Jagdtiger, T30, T95, Jagdpanzer E100, Waffentrager auf E100, T110E4, FV215b (183), T110E3
Artillery - US Sexton I, Birch Gun, AMX 13 105, M41, M12, M40/43, M53/M55