I don't see any armbands on that Agumon, so its not Masaru's Agumon.
For simplicity's sake, we'll just assume they're a generic Agumon and Charmeleon. In that case, with no evolution allowed, it depends on the Charmeleon's moveset. Agumon only has two attacks; breathing small fireballs and its claws, so the Charmeleon can beat it through sheer versatility.
I don't see any armbands on that Agumon, so its not Masaru's Agumon.
For simplicity's sake, we'll just assume they're a generic Agumon and Charmeleon. In that case, with no evolution allowed, it depends on the Charmeleon's moveset. Agumon only has two attacks; breathing small fireballs and its claws, so the Charmeleon can beat it through sheer versatility.
The scales would fall toward Agumon's side.
Even assuming they're both flesh-and blood creature Agumon still have less weakness compared to Charmeleon. Let's break it down, shall we?
Head: Agumon wins per skull structure, biting force and mouth size. Tyrannids has thick skulls with a lot of surface area that can absorb blows AND prevent sneak attacks to the neck, powerful jaws that can deliver a mean bite compared to large jaw to hold prey in place. Combine that with neck muscles strong enough to keep that large, unwieldy head stabilized and you have enough tools for tearing flesh in one bite.
Compare them with Charmeleon's mouth, which is not specialized for tearing but biting (in this case, the teeth structure looks closer to large felines or canids) into a prey's weak spot, most likely jugulars.
Arm: Charmeleon wins by having longer reach and opposable thumbs. It allows for grabbing into the opponent, unlike Agumon's 'hand' which serves as secondary front foot.
Body: Agumon wins (yes, despite being shorter and smaller) by having a lower stance than Charmeleon. Anybody doing martial artist would've known how hard it is to aim low when fighting opponent shorter than you; you need to lower your stance, thus limiting the choice of moves you can perform. Kicks are the easiest way to get countered and slammed down as counter, and lunging on your opponent is another no-go strategy.
Tail: You'd think Charmeleon wins this round, but no. Tail whips are virtually useless unless you either have enough mass and biological weapons, like Stegosaurus' thagomizer or Ankyloceratops's bone spurs, and that's not mentioning the damage you take in recoil-tails are not made of iron, after all. Not to mention, Charmander-kind shares the same weakness: extinguish the flame on the tip of their tails and they'd die. Agumon's tail is virtually useless and would be just a weakspot for biting/scratching attack, but at least it didn't have OHKO function built-in.
Leg/Speed: Any speed advantage Charmeleon have are invalidated because this isn't a running match, this is a brawling/wrestling match. At such, the best it can do with those legs are using the talons to inflict cuts while holding the enemy with it's arm, a tactic that Agumon can't do. Agumon's strategy given it's body was 'charge, topple enemy, take a bite' since it's body structure made grappling virtually impossible with such short limbs.
Special ability: Tie. Both resists fire-based attacks, so at best their fire breathing would just be distractions to create openings.
Who would win, then? Charmeleon's winning condition would be far harder than Agumon's: it needs to flip Agumon on it's back and deal mortal blow on either the stomach or neck area, where Agumon's winning condition is far easier: it just need to catch any body part in it's mouth and bite it off. Ergo, Agumon would probably win as long as they're just using fire-based moves (Charmeleon learns Dragon Breath naturally, which can paralyze enemies).