The headword noun is here in the dative plural, evidently quoted from somewhere; there are several extant possibilities. The glossing follows Photius, Lexicon pi5 Theodoridis (with other references there), though 'boxers' is here expanded.
Although boxers did participate in the pankration (pi 11), the pankratiasts competed in a separate event, one that shared striking with boxing and gripping and falls with wrestling. This Suda entry describes them as a kind of boxer but they were also a kind of wrestler, both kinds then adding up to the unique entity, the pankratiast.
According to Philostratus, "perfect competitors for the pankration are those who are more suitable for wrestling than boxers and more suitable for boxing than wrestlers" (Gymnastic 36). On the other hand, pankratiasts did not need the size of the wrestler or boxer to be successful. One athlete, for example, whose father called him Halter or Jumping Weight, evidently because he was small, used the tactic of seizing his opponent's heel and not letting go until he submitted (Philostratus, Heroic 52-54). The jumping weight, a stone that jumpers held in propelling themselves through the air, suggests that Halter was compact, strong, and lively. On the positive side, pankratiasts became a byword for concentration:
"The life of men who spent their time in the midst of affairs and who want to be of use to themselves and their people brings problems and dangers suddenly, continually, and nearly every day. To be on guard against them and to evade them, such men must always be alert and focused like those athletes called pancratiasts. Just as these athletes, when summoned to the match, take up a position with their arms held high and stretch forth and protect their head and face by presenting their hands to their opponent like a rampart, and all their limbs, before the battle has begun, are on guard to avoid blows, the spirit and mind of the prudent man ought to be focused" (Aulus Gellius, Attic Nights 13.28).
On the other hand, their tactics brought down upon them the stigma of being lions:
When Demonax saw many athletes fighting dirty and biting against the rules instead of engaging in the pankration, he said: "With reason, the fans of today's athletes call them 'lions'" (Lucian, Life of Demonax 49),
while their reliance on kicking invited another odious comparison:
"Do not respect, faith, and justice exist? Show yourself better at these in order to be a better man. Should you tell me, "I kick a great kick," I will say to you: "You boast of a accomplishment that belongs to an jackass" (Epictetus, Discourses 3.14.14),
The most famous pankratiast of them all was Arrachion or Arrichion who died, probably by his own doing, in a match during the 54th Olympiad (564 BCE). Both Pausanias and Philostratus give an account of his final match:
"Arrachion won two Olympic victories before the fifty-fourth Olympiad [564], and another came his way in the fifty-fourth because of the fairness of the Hellanodikai and Arrachion's own courage. When he was fighting for the wild olive against the last remaining competitor, whoever that was, his opponent gripped Arrachion first and held him in a scissors hold with his legs. At the same time, he was pressing on Arrachion's throat with his hands. Arrachion dislocated his opponent's toe but expired from the choking. The one choking him at that moment acknowledged defeat because of the pain from his toe. The Eleans proclaimed and crowned Arrachion's corpse as the victor" (Pausanias 8.40.1-2).
Philostratus' account is a description of a painting that he sees while touring a picture gallery with a young friend. Acting as the wise instructor, he explicates the portrait for his companion:
"You have arrived at the Olympic Games themselves and the noblest of the events in Olympia, men's pankration. Arrichion is being crowned, although he died in victory, and the Hellanodikes here is crowning him... For now, let us look at Arrichion's deed before it is over, for he seems to have conquered only against his opponent but the Greeks in the audience. In any case, they are leaping up from their seats and shouting. Some are waving their hands or cloaks, and others are jumping into the air. Others are pounding their neighbors on the back in joy. The spectators are seeing something so amazing that they cannot contain themselves. Who is so unfeeling that he doesn't cry out at the athlete? This accomplishment of his is greater even than his great deed of winning twice before at Olympia, for this victory came at the price of his life, and he is being escorted to the Land of the Blessed with the dust still on him. Do not think that victory happened by accident. No, he figured out very cleverly the move leading to victory... Arrichion's opponent, having already grasped him around the waist, has decided to kill him. He inserted his forearm on Arrichion's throat, blocking his breathing. He then fit his legs around Arrichion's groin and passed the ends of his feet through [Arrichion's legs] and pressed one against the bend of each knee. Because of the stranglehold, Arrichion's opponent got ahead of him as the drowsiness of death was creeping over his senses from this point. But his opponent, in relaxing the pressure of his legs, did not get ahead of Arrichion's stratagem. Arrichion kicked back the sole of his [right] foot. His right side was threatened as his bent leg was left dangling. Arrichion gripped his opponent with his groin so that he no longer resisted. Then throwing his weight to his left, he locked the end of his opponent's foot in the bend of his knee and, with a violent wrenching outward, he did not allow the ankle bone to remain with the ankle. His spirit, departing his body, acted listlessly but gave him the strength for what he aimed at doing. The strangler is painted in the picture to look like a corpse. He is acknowledging defeat by his hand. Arrichion is painted in the way victors always are. His blood is in flower, and his sweat is still fresh. He is smiling just as the living when they have become aware of victory" (Pictures in a Gallery 2.6).
Robert H. Brophy, III ("Deaths in the Pan-Hellenic Games: Arrachion and Creugas," American Journal of Philology 99 (1978): 363-390) presents a convincing case that Arrachion killed himself by breaking his own neck:
"Anatomically, Arrachion's head should have led or accompanied the leftward thrust of his body as he kicked up and back with his right foot, but his opponent was holding it immobilized. The snap of his fall or leap sideways, while his opponent still retained his strangle hold, caused the same effect as death by hanging: the fracture of the dens of the axis bone, severing the vertebrae from there down" (381).