Magnemite is the (2nd) best Pokemon in the game and if you disagree I will fight you irl. There is no way this thing is not the (2nd) best.
Availability: Trainers' School. Relatively high encounter rate, easy to catch.
Offense: Thunder Shock sounds dumb but off Base 95 SAtk it steamrolls ****. I hear some people saying "oh no!!! thunder shock doesnt do **** in akala" well GUESS WHAT it gets a Magnet in the Pikachu Valley and the Charge Beam TM at Brooklet Hill (or so I've heard). That's a 50% increase in damage output and right before the Water trial!!! insert multiple thinking faces here. Then it evolves probably by the end of Akala, and AGAIN once you reach Blush Mountain (not that far away). Now you have a Magnezone vs scores of NFE garbage being thrown at you, gg
Defense: Being part Steel-type means you not only beat every Melemele trainer not named Hala, but also every Team Skull Grunt (makes a convenient lead versus them). AND half the trials: Gumshoos/Raticate, Togedemaru (use Hidden Power lol), Mimikyu, and Ribombee. Basically simplifies a lot of the game. ALSO you can use it to get a Toxic off on Ultra Necrozma = ezpz
Design: a better Electric-type than your Rotom Dex. bzzt!
There is absolutely 0 way this mon is not the (2nd) best Pokemon in the game.
Credit where credit is due: https://www.smogon.com/forums/threads/ultra-sun-ultra-moon-in-game-tier-list.3621876/page-3#post-7601415