Dreading a Focus Blast Mewtwo
I ran some sims on pokebattler against Mewtwo with PC/FB and C/FB. No dodging setting. Level 38.5 attacker and level 40 Mewtwo. All perfect IVs.
Against PC/FB, the best counters in order were Gengar SC/SB, Dragonite DB/O plus all other good MS, and Gyarados B/C. As expected, dark types like Tyranitar, Houndoom, and Umbreon got demolished.
Against C/FB it got ugly. Nothing beat Mewtwo. Houndoom S/FP damaged Mewtwo the most before fainting, then Scizor FC/X, then Houndoom S/C, and then Dragonite DT/O.
Need to get me some more Houndooms. Shit gonna get real when we face Mewtwo C/FB. Y'all ready? Hahaha
Edit: I must be high. Forgot about Exeggutor. BS/SoB got best result against C/FB. ??♂️
Answers
The one silver lining here is that Focus Blast is slow, really slow, slower than Earthquake, Hyperbeam slow. So dodge it, and dish as much DPS otherwise as possible.
What about Gengar SC/SB? Or Hex/SB? Double resist fighting and do all Ghost damage. And of course, Mewtwo with Shadow Ball should crush Mewtwo with Focus Blast (although that's cheating the simulation).