One of the most underrated tornado outbreaks is the May 7-10, 1927 Mississippi Valley-Plains tornado outbreak. This outbreak consisting of >35 significant tornadoes and >9 violent tornadoes (I also looked through newspapers for weak tornadoes and came up with a total number of at least 66 tornadoes) affecting an area extending from Northern Texas, to Nebraska, through AR/MO/IL, and all the way to Northeastern USA. 217 people were killed as a result of this outbreak. I'll talk about some of the most notable violent tornadoes of this outbreak:
New Bloomfield MO F4
This very violent tornado devastated rural areas west of New Bloomfield, sweeping away multiple large homes. One house the tornado encountered was anchored to its poured concrete foundation with 1/2 inch iron bolts. The tornado completely leveled and partially swept away this home, tearing loose a 16x6 ft and 4 inches thick chunk of concrete which broke into 3-4 pieces. 3 people in the basement were killed when the concrete chunks fell onto them. Large trees were snapped in half, uprooted, or carried several hundred feet.
Nevada TX F4
This tornado was a part of an erratic and violent tornado family that struck the NE Dallas metro area. The western half of the town of Nevada was leveled along with farms in rural areas. 19 people were killed as a result of this tornado. Not much information is available about this tornado.
Greenville TX F4
The second violent member of this tornado family cut a 15 mile long path in NW Hunt County. Even less information is available about the tornado but it reportedly swept away farmhouses. 6 people were killed by this tornado.
Garland TX F4
This tornado cut a 1-mile long looping path in NE Garland. Despite the destruction occurring only in a 5-block area, 15 people were killed by this tornado. Homes were completely leveled.
Poplar Bluff MO F4
This was the deadliest tornado of the outbreak that struck Arkansas and Missouri. 15 homes were destroyed in Arkansas at F4 intensity. The tornado wasn't exceptionally intense when it struck Poplar Bluff but due to the downtown area being packed at the time, it became a mass casualty situation. 98 people were killed, 93 people in Missouri, and 5 in Arkansas.
Strong AR F4
This extremely violent tornado devastated the town of Strong. A large part of the downtown area was literally leveled to the ground and the "best homes" in town were swept away. 24 people were killed.