ralentizar
slow down
relent
become less severe or harsh
+
-izar
to make or become
Ralentizar means to slow down and can be thought of as relent0 (become less severe0) + -izar1 (to make or become1), essentially making something become less intense or slower.
verb
  1. slow down
    To slow down or decelerate
    El tráfico ralentizó nuestro viaje. // The traffic slowed down our trip.