>>55271068Onix being a rubbish "first boss" monster isn't so much of a problem as the fact that it's shit at being a boss monster too. It can't hit for shit, has two QUAD weaknesses that two of the three starter pokemon can exploit, and it has a crippling Special stat hole that makes ember a viable option, low effectiveness be damned. In gen 1, Tackle doesn't do shit, Screech misses 50% of the time, and using bide means Onix has to risk taking super effective or special attacks for 3 turns. They fixed it somewhat by giving Onix Rock Tomb, which has STAB, is super effective on fire and flying, and slows you down if it hits, so it could thereotically get a 2HKO before any meaningful chip damage could be done by Pidgey or something. If Onix had significantly more Special or Sp. Def in later gens, it would bump up the shittiness.
I want to cite an example of a first boss monster done right with Roxanne's Nosepass. It's a weak piece of fodder compared to everything after, but for early game it has a sky high defense stat, a respectable special defense stat, and no quad weaknesses to water or grass. Nosepass and Onix have the same attack stat, but Nosepass can actually take a hit and throw back rock tombs until it outspeeds and kills Tailow or even Treecko if the player is unlucky.
First bosses aren't meant to be super difficult or be crazy, but they shouldn't be free either.