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I got to round 63 in Super Singles today.
All you need is Mega Kangaskhan. The CPU can't cope with Sucker Punch in 90% of cases. Kangaskhan didn't even faint on the Round 50 match against the three genies. Oh, and make sure to run max HP/max ATK, so you'll survive that Landorus' Focus Blast. (The Landorus is a special attacker, and the Thundurus is physical, so keep that in mind)
Your other two Pokemon are filler, but I recommend something with Focus Sash and something with Choice Scarf. (I had Sash'd Speed Boost Blaziken and Scarf'd Garchomp, but they didn't do much overall.)
And if anyone's wondering about BP stuff:
You get 50 BP for beating Round 50.
You get 7 BP per match for every match following 50. It does not increase past 7 after 10 rounds, so it's safe to assume it never increases again.