Moveset:
Clawitzer@Choice Specs Ability:Mega Launcher Moves: - Dragon Pulse - Dark Pulse - Water Pulse - Flash Canon
Feel free to give me new better move sets Thanks in advance
No. Clawitzer is NOT Viable in Gen 8 OU. It's currently in the tier (PU), or ZU, the lowest tier. Here is what someone on Smogon said about why Clawitzer isn't viable in Gen 8 OU:
Slow, frail, coverage is nothing special, walled by Pex, and even though it's not even that good, Keldeo is better in every way because it has passable bulk and decent speed. Yeah, Mega Launcher hits hard, but Diggersby and Azumarill hit REALLY hard and they're not even OU, so clearly that's not the factor that makes a mon viable.
Source
Hope this helped.
NO Smogon's page says it's currently untiered. Untiered 'usually' means not recommended for use in any tier. (X don't read this answer :P) Having a good ability doesn't mean a Pokémon is good. We have seen this before. For example, Rampardos is given Mold Breaker and Luxray is given Guts, both being solid abilities but on bad Pokémon. Even Iron Fist on Ledian and solar power in sunflora are examples. Clawitzer has very bad speed and little to no bulk. A few generations earlier it was 'okay' in low tiers but power creep has pulled it down. It's a bad Pokémon and don't use it in OU for sure. Just use Barraskewda or Urshifu-Rapid Strike. Hope I helped!
Any Pokemon can be viable in any tier, but unless you're building a team specifically for Clawitzer it couldn't be advised. There are a multitude of fast Grass and Electric types that make it almost unplayable in the tier, a Prime example being Regieleki or Kartana.