Combat sports are inherently dangerous, even with modern medicine, and many fans of pokemon battles can recall a time when they witnessed a pokemon die in the ring. Primeape, whose angry and fearless fighting style often allows them to participate at higher levels than their defenses would justify, are particularly vulnerable to this fate. And yet trainers and fans need not mourn, for like Dartrix, death is a requirement for this pokemon's evolution.
The popular claim that Annihilape are born when a Primeape becomes so angry that it suffers a fatal aneurysm can not be proven, for any increase in fury beyond the extremely high level already typical of that species is beyond human ability to measure. What can be confirmed, however, is that it is their rage which binds an Annihilape's spirit to this realm; any competitor is bound to lose occasionally, and these pokemon take defeat particularly badly. Annihilape are not necessarily poor sports, and are more likely to blame themselves or their trainers than their opponents when they lose; this does not, however, make them any happier about losing.
One might think that victory, then, would calm Annihilape's spirit, and perhaps many departed this way in the distant past. Yet in the modern, international era of competition, there is always another, bigger tournament, and trainers are no more eager than their pokemon to allow their prized fighters to move on. Only one Annihilape is known, as of this writing, to have actually left this world, its spirit finally pacified; it departed a world champion.