Defuse & Diffuse

With an E – (v.) literally, to remove a fuse. Metaphorically, to make a situation less dangerous.

With an I and two Fs – (v.) to scatter or spread thinly.
(By the way, the adjective form of Diffuse has essentially the same meaning as the verb, but is pronounced with a hard S sound at the end, rather than the Z sound used here. Homographs!) :)