Iancu de Hunedoara. Romanian ruler that allied with the Hungarian Empire (the wiki page may be full of crap, there is historical animosity between us and the Hungarians which leads to bad wiki pages on common subjects)

http://en.m.wikipedia.org/wiki/John_Hunyadi

He died of the plague which he contacted during a militari campaign south of the Danube, in modern-day Bulgaria.

The impact was globally non-existent, but locally it meant a return to worse relations with the Hungarians (which in all honesty we wanted).

Edited for clarity

I'd like to add a follow up question if that is alright.

How did these deaths impact the change of power during this time period? Did political deaths have an impact on Europe that would be measurable in economics, borders or alliances?