@Longhatruong
I understood you literally meant stronger, but I see you actually meant capable of defeating one. About that, not really.
To begin with, Bell was faster, but not by big margin. And I do not mean it just because of the numbers, but in regards to performance as well. Bell barely managed to dodge and intercept attacks. He was also using a trick he learned from Ais in that by hitting the side of the blade he gave himself space to slide past its attacks.
So Bell's dodges weren't a matter solely of speed, but he was using technique as well. Furthermore, even then the problem was that fighting like that was quite dangerous, as it is described as a method that leaves no room for error. Of course, it does mean there is a possibility that a Level 1 with an agility stat basically in the S999 limit pulls this strategy off, but even then that's not all there is to it.
Another issue with the Minotaur is its resilience as it is mentioned that, even if a weapon pierces its skin, there is a good chance it would get stuck in its muscles due to how dense they are. And well, losing your weapon against such a threat is pretty much a death sentence.
The Hestia Knife actually helped with that too. It being Bell's only weapon actually capable of injuring the Minotaur made it be wary of it, which Bell even used to perform a feint in order to take its sword and therefore actually start to hurt it.
And while the Hestia Knife grows alongside Bell, it does not mean its quality is just as good as his level. In DM18 for example it endured a clash with Ottar's sword despite the two levels gap. Meanwhile the Minotaur easily destroyed Bell's baselard despite it proving useful against all Level 1 monsters Bell fought.
So Bell had going for him his speed, technique and weapon. Besides speed (as you mention a theoretical full S999 adventurer), considering how big of a deal Ais' training is meant to be it is at the very least debatable if a regular Level 1 would be as skilled. And a regular Level 1 is also definitely not going to have a high class weapon either.
Personally I'd still say the Minotaur is "overall" basically a low Level 2 monster. I mean, even the Guild says rank G is good enough to navigate floors in which they appear. Having strength and endurance stats within the same league definitely helps, though I'd assume that the speed gained from being Level 2 is the major factor (all attacks are useless if they just can't land).
Ultimately Bell's fight was an anomaly. What allowed a small opportunity of victory was that, for as much of a Level 2 the Minotaur is, its speed is still Level 1 tier. And Bell was a completely extraordinary Level 1. This is just my take, but if the Minotaur actually had Level 2 tier speed I don't think Bell would have stood a chance.
So I'd say it depends in what you mean by "weak Level 2". If you mean a monster who is overall a weak Level 2, but whose abilities are nonetheless all Level 2 tier, I don't think a Level 1 could defeat it. But if you mean one who has at least one Level 1 tier "stat" (maybe specifically agility), then there is a slim chance. So long as you get a really, really good Level 1 that is.