This is a rather easy one to figure out.
One can wreak havoc with things that reek. =P
Reek is a smell, nasty, but a smell nonetheless
To wreak is a verb; it is something that someone does to something else. It is also not to be confused with “wreck,” which I have actually seen before.
Rusty’s litter box reeked from lack of cleaning. Whoopsies.
Rusty wreaked havoc in the middle of the night when I was trying to sleep; the darn cat never wanted me to be fully rested.