[There's one in all but one word. That has to be a contender.]

tweaks

Testy whiner evades killing stroke.

whiner

whiner

When he investigates, Noir establishes regret.

regret

regret

Rancid excuses get recycled every time.

rancid

rancid

Rats are now common in Detroit.

common

common

Cats only meow. Mice only nod.

unreal

unreal

Urban neighborhood rodents eat a lot.

rodent

rodent

Rodent overlord dines exclusively near turret.

turret

turret

Tiny upper rooms reconnoiter entire towers.

entire

entire

Even nerds tear into respected elders.

elders

elders

Every lovely diamond engagement ring sucks.

cartel

cartel

Calling all retrograde teachers. Expect less.

expect