...The Harder They Fall

...The Harder They Fall is an achievement/trophy in Fallout 4.

Requirements
Kill five giant creatures. The only two enemies that count for this trophy are super mutant behemoths and mirelurk queens.

If you are travelling with a companion, you must be the one to fire the killing shot in order for it to count towards the trophy.

Super mutant behemoths

 * Outside of Fort Strong.
 * West of Natick Banks.
 * In the woods south of Greentop Nursery and east of Malden Middle School. Only spawns after removing a Jangles the Moon Monkey toy from a car crashed into a tree. However, when ordering companions to grab them, the behemoth does not spawn.
 * West of the Suffolk County charter school.
 * South of Walden Pond at a car-like Stonehenge.
 * Swan is a unique super mutant behemoth and can be found at Swan's Pond at Boston Common.
 * South of Recon bunker Theta.
 * Random spawn in front of the Super Duper Mart in Lexington.
 * During the quest Ad Victoriam, one will spawn on the way to C.I.T. ruins before being killed by Liberty Prime.
 * Grun is another unique behemoth and can be found inside the Vim! Pop factory.
 * In a small gulley to the northwest of Dry Rock Gulch.

Mirelurk queens

 * At the Castle as part of the quest Taking Independence.
 * At the Murkwater construction site, must be defeated in order to use the area for settlement.
 * Spawns at Spectacle Island once throwing the circuit breaker.
 * At Nahant Chapel, nesting near the coast.
 * In the basement of the Massachusetts State House.
 * South of Warwick homestead and east of the Poseidon Energy plant, close to a capsized boat in the swamp.
 * To the west of Salem, northwest of the Museum of Witchcraft.
 * By the beach just southeast of Revere Beach station.
 * Southeast of Recon bunker Theta.
 * In the lake by Northpoint reservoir.
 * In Vault 88, in the water by the water pump. Appears after defeating a small group of mirelurks.
 * At Emmet's Causeway as part of the quest Rite of Passage.
 * At Northwood Ridge Quarry.