Top 10 things to do after finishing the main quest

[Melekler]

I finished the game and i would like to to other things

[callmetone]

Get all the bobbleheads, get all the magazines, work on the achievements, explore all the extra buildings around the Commonwealth and pick up the side missions, or mess around with mods like most people. If you haven't played in Survivor Mode, try that.

[Drake Ravenwolf]

Really dig into the settlement building; eg resorting Sanctuary or the Castle

[casualsailor]

Explore. Walk everywhere. You'll be surprised at how many locations are not FT destinations. There are literally hundreds of abandoned houses and buildings. Many of them have terminals or dead bodies with notes which are clues to minor mysteries or caches. And lots of enemies, deathclaws and mutants to kill.

Radio beacons are meant to be followed. These have mysteries to discover. Some are just, what happened to a family but some require you to navigate to and solve other parts of a mystery.

Find robot race tracks, deathclaw arenas, a behemoth cage made from old cars.

Do the radiant quests for the RR if you can. Finding your way to the tops of the buildings to plant MILAs can be fun. Most rooftops are accessed by combinations of catwalks and thru nearby buidings making this a maze/platformer to solve.

Do all the companion quests. Most have pretty good stories.

Chech your Misc quests and dump your Misc items. Any item associated with a unsolved quest cannot be dropped. You'll be surprised how many notes, tapes or other items you have onboard that you picked up already.

Explore the subways, basements, bunkers and every building downtown. They are full of small stories of either pre-war people or the raiders. Read the terminals and listen to the tapes for clues.

Explore the Quincy Ruins and the Glowing Sea. You didn't go to QR for the main quest and only a couple locations in the GS. There's other stuff to find there. QR has no quests but yet this is where the Minutemen came from and their betrayers are still there. After you clear this area and find all the notes you'll probably feel like me that there was a MM questline here that was planned for a DLC or cut for time. There's just too much work put into this area and the people for there to be no quests at all. So, get some revenge for your MM brothers.

[callmetone]

Also, the DLCs are not part of the main storyline. The mechanist, Vault 88, Far Harbor, and NukaWorld are pretty challenging. Some people seek out all the abandoned power armor suits and paint jobs and create a collection.

[Arash The Great]

Get all affinity bonuses from companions ( reach high affinity with companions ) !
Play DLCs
Make your settlements sexy ( I mean good looking )
wander around the wasteland
Collect bobbleheads , magazines
Loot stuff and trade with traders
Find power armors
Find atom cat garage for making your power armor badass
Explore locations especially dunwich borers if i wrote it correctly :]
And also if you watch oxhorn's videos , there are many small stories for places , for characters everything :D try to find them on your own
Create new characters and try survival modes
Install some mods ( especially story mods )

[Wolli Wombat]

Get the mod "War for the commonwealth" (or how it is called?) and then fortifiy your settlements! Survive in the darkness!

[Mad Max RW]

I highly recommend Far Harbor. Remember to grab one of the Nexus mods that remove or greatly reduce the amount of fog.
https://www.nexusmods.com/fallout4/mods/14447/?

Nuka World is alright, but it requires a fan patch and a proper ending available here:
https://www.nexusmods.com/fallout4/mods/17853/?
and here: https://www.nexusmods.com/fallout4/mods/18121/?

If you have a monster of a PC and want to transform the look of the whole game I fell in love with the Regrowth Overhaul mod: https://www.nexusmods.com/fallout4/mods/9656/?
It looks less late fall and more late summer. With all the vegetation the world actually feels bigger.

[zipiffect]

destroy the entirety of diamond city