Would this be too hard for a third gym leader?

I have been coming up with the gym leader teams but I'm wondering if the third one is too hard. He has four Pokemon, with them being Lv20-21 and they are Steel type. The third gym is a Steel type gym because the city it's in is based on Pittsburgh (the region is based on the Northeastern US), and you start in the southern part of the region and head north. His team has a middle stage Rock/Steel type fakemon, a Metang, a third mon that I am trying to decide, and his ace is a pure Steel type. However, I'm wondering if his ace would be too hard to beat. This is his ace



Ankylosteel Lv21

Type: Steel

Gender: Male

Stats

HP: 95

Attack: 90

Defense: 120

Sp.Atk: 50

Sp.Def: 90

Speed: 45

Total: 490

Ability: Solid Steel (Steel type version of Solid Rock, though every super effective move does 1.5x damage, even if the Pokemon is four times weak to the move without the ability. The ability was originally intended for the Rock/Steel type fakemon I mentioned earlier, and the gym leader has the ability on it too, though I also decided to give it to Ankylosteel)

Item: Sitrus Berry

Moves

Magnet Bomb

Bite

Dragon Tail

Iron Defense

You do have some counters. If you didn't pick the Fire starter, there are some other Fire, Fighting, and Ground types you can get. You also have access to a few Water and Electric types at this point, with the Water starter being Water/Electric. There are also a couple Dark types you can get to deal with Metang. Depending on the Pokemon, they might still be unevolved due to the level (example: the only Ground type fakemon I have thought of doesn't evolve until Level 26). Would this be too hard, and if it is, how could I change it?

I appreciate a good challenge, so if the player truly does have counters for the Gym, I see no issues! Gym Leaders are supposed to be tough and make the player use strategy instead of one-hit KO-ing the whole team.

Personally, my next game will include Water Absorb on the first Gym, so I can say that'll be tough on its own. You'll need strategy!

yes, too hard
try giving the fire starter Wil-o-wisp around lv.20
it's a physical attacker with medium attack, so a Burn would make it much less threatening & the player can slowly take it down.

Are there any type-advantaged Pokemon that are specially-oriented? Are they also physically defensive?

As long as the player has ways around it, it's fine imo.

Really, the only way to know if a boss fight in a game is too hard or too easy is to playtest it, imo. There are so many variables that go into it that it's almost impossible to know if it'll be too hard or too easy without trying it yourself, or getting a friend to play it for you, plus you never know what pokemon the player is gonna use, that alone could make it very easy or very hard. Try starting the game from the beginning and just play through till you get to the gym leader without grinding too much and see for yourself if it "feels right". Also, like others said, there's no rule against having your game be difficult! This is gonna be a game for pokemon fans anyway, so, it's a good excuse to ramp up the difficulty a bit, the official games are aimed at children, after all, and it'll probably be teenagers and adults who play yours! Also if do decide it's too difficult, there are tons of ways to deal with that in an RPG, you could always just lower the levels but keep the moves/abilities the same or vice-versa, or you could put a trade in the town that gives a powerful Fire pokemon, lots of ways to adjust difficulty in pokemon games :D From what you described it (subjectively) sounds ok, though!

I'm not sure if I'm too late but no that definitely doesn't look too hard