By Harry Davies Olympic bronze medalist Robelis Despaigne, who stands at 6ft 7 and weighs almost 120kg, won his UFC debut by KO in just 18-seconds. Despaigne, 35, won bronze in taekwondo at the 2012 London games and is now an unbeaten MMA prospect over a decade later. The Cuban put on a stunning performance in his promotional debut at UFC 299 on Saturday night in Miami, knocking out Josh Parisian just seconds into the opening round. Despaigne had Parisian on the retreat as soon as the fight started and he missed a big uppercut before falling on his backside after attempting a head kick. Parisi…