The fighter is not necessarily more threatening. They are more skilled. They dominate the field.
I've been involved in four donnybrook-equivalents in my life (to what should be no surprise, three came on the basketball court...which is one of the more dangerous places in the 1st world imo!...the other was a bench-clearing-brawl in baseball...which is almost exclusively just male peacocking and no action.).
The three on the basketball court were all enormously dangerous situations that I didn't want to be in (and certainly didn't start). Dealing with two to three able-bodied, testosterone-fueled, fighting-age males leads you to have a better understanding of what this situation looks like. At the point in my life that these events occurred, I wasn't new to this kind of thing and I was in grappling and BJJ for many years so it wasn't terribly difficult to assess who was the most dangerous person and/or what was the most dangerous dynamic.
In one of those situations, the primary thing that drew my attention was the guy that instigated had been relentlessly goading me (totally looking for a fight from literally the moment he came into the gym...the fact this occurred was zero surprise; I predicted it would happen to my friends before it did), physically and verbally, for a good hour. Things set off when he goaded me into a fight with a huge cheap shot and then running his mouth. No matter how poised of an individual you think you are, when someone chest-passes a basketball at your head (as hard as they can) from the side when you aren't looking and then immediately is mouthy about it, that is the person who is going to have your attention (even if his two buddies are jumping you).
In the other two it was a combination of who pressed me and who presented me with an opportunity to attack their legs to initiate a grapple which would, in turn, allow me to control them while using their own body to protect myself against their friends (ok, you want to stomp me, kick me, or punch me while I have your buddy's back...have at it...but he's going to eat the collateral).
There is an easy lesson to draw here on what a donnybrook would look like when it comes to a D&D Fighter and its exactly what you've written above:
* The most
skilled at goading (via signalling which can be cheap shots, feints, actual words, or the combination).
* The most
skilled at presenting as dangerous/threatening (even if they aren't the most dangerous/threatening).
* The most
skilled at pressing the action, managing distance/connection, and forcing a decision upon you (if I don't try to initiate a grapple or engage with this person, I'm perhaps losing an opening or creating an opening for them or another person that I'm going to regret).
That is the skillset of melee control (Defender suite) that a D&D Fighter would possess within the dynamics of a donnybrook. It just so happens that the D&D Fighter can also kick the hell out of you at the same time (its not just Advanced Peacocking +).