Fallout 4 is a pretty good game overall. A lot of content, pretty good combat variety and a leveling system that makes customization easily accessible. If you play your best in the game its really easy to become strong and not ever really be in any danger to die. This happens because of the amount of experience you receive from doing mundane things like visiting new places. If you do any settlement building its easy to have 100 pure waters in your inventory at any time and unlimited ammo. With survival mode the player is constrained by mechanics like nutrition requirements and the enemies are more difficult but the game itself just seems more tedious. Not having fast travel is annoying, having to walk across the wasteland is not a challenge its a tedious task that is now added to every quest. Eventually even in survival mode its possible to get extremely strong and durable. This is actually a core feature to an rpg. You should always allow the player to farm up so they are never in danger of not being to advance the story. I think the "very hard" mode is actually challenging enough in terms of enemy difficulty but doesnt have the annoying necessity for food and still has the convenience of fast travel. There is a way to play this game which keeps the challenge going that focuses on character build for the action. I want your build to require you to use all your stimpacks, ammo and nukacolas. This is the sign of you being challenged, when you need to use all your resources.
Ill layout two different play styles. The first style is the long battle sequence style. Here you want to focus on making yourself durable but not focused on being too damaging. This way to get long fire fights and your aim will be important as youll be using a lot of ammo. This challenge focuses on your skill to dodge and aim effectively. The second style is a glass cannon style in which any mistake gets you killed but you do so much damage you can pick off enemies as fast as you see them. This style focuses on your skill to setup the proper attack and making good choices on who to kill first. Both styles have perks you want to focus on and perks you want to avoid. In the end Ill make general comments on things to avoid that cause the game to become too easy.
Focusing on being durable and not doing tons of damage. This style you want fights to last 5 minutes take 5 stimpacks and require tatics, not just running through a warehouse and picking raiders with a shotgun one by one never in danger and never having to use 1 stimpack. You are going to want to do a mix of these tailored to your character. Doing all of them will probably just make you indestructible.
Avoid bloody mess and other luck perks unless you feel you are not doing enough damage. I would also suggest you stay away from explosion perks as these items are already really good and adding damage to them will make the game too easy and your tank character will just become a mobile artillery. Keep your damage low and your tankyness high and enjoy mixing it up with the raider gangs. Pop some psychos for extra damage during boss fights.
Focus on doing a lot of damage, trying to stay undetected, and being fragile yourself. In this style you want fights to last 30 seconds and will require you to setup, get the drop on the enemy and choose enemies to kill wisely. Stimpacks wont help much here because youll lose all that health with one shot.
Stay away from endurance perks and in general keep your endurance low. To keep the game challenging in this style of play you need to give the game as much chance to kill you as you have against the enemies it spawns. Youll find a lot of your deaths are unexpected, but remember that this is a double edge sword and youll probably find a lot of instances where you didnt expect to kill an enemy so easily.
In general play the game fast , try to beat the game at a low level. After lvl 40 your character will have loot and skills to make it easy on any difficulty and this is how a rpg should be (it should just take some time). I rather be able to farm up to god level then have the Oblivion problem where you are never strong because enemies always match you. Dont get too much experience from doing easy stuff like settlement building. This will make you level faster making the action easier. You want to level through combat. That way you experience how tough it is and also will force you to use items at a lower level which means you have to be smarter with those items (when to use stimpacks, chems , conserving ammo). Another easy way to challenge yourself is to set a cap to how many chems and stimpacks you can use in any battle or dungeon if you need to use more than this means you are relying too much on items to get through a fight and not your skills. Don't get idiot savant, it just a excuse to make the game easier for doing nothing. Lastly here are a couple of console commands that you can run that will make the game more difficult.
player.setav 357 .5 (this is drop the damage you do by 50% , default is 1)
player.setav 359 50 (this will drop your ap regen rate by half , default is 100)
