Seedling Runt - Stay or Go?

Never throw out runts at this stage, it could be the new hypiest hype cut! You'll see in a few weeks if it's a weakling or not. FYI you should never aim for long stems on seedlings, you'll want to keep them as short as possible so they can support their own weight, make sure they get enough light and they'll stay short and grow thick and strong :)

looks and is small but it will grow :)

consider a smaller 'first' pot-up. if it doesn't stay wet for 7-10+ plus days, not so bad. Otherwise, just stagnating nasty ass water for 7-10+ days.

This plant doesn't look defective, and if anything you potted up on the early side, not late. It may not grow as much above ground, initially, but lots is probably happening in the root system. you've got a fairly small plant in a slightly too large pot, so once that tap root hits bottom, you'll see above ground growth pick back up. Wait longer for that first pot up. Make sure the rootball is established. The root system and some minimum moisture should easily hold the substrate together. Depends on context... I plant 2x as many as i need so i can kill the weak. This makes for a more consistent outcome. I kill anything that is defective or slow. Don't care if it might have produced a half-yield of high quality bud, lol. If it's missing 1 of several improtant traits, it's trash to me all the same. YMMV If you only planted enough to fill the space, then you keep it since the space would be wasted if you didn't. Easy choices... again, don't think this applies here unless it's fallen far behind other plants. laggards cause logistic issues and sacrifices to other plants.. which results in reduced production.

No she is about to be established and take off...be patient.