Although these are far from the most difficult achievements to unlock, they can be quite annoying. That's why I decided to post a much simpler and easier way that I found out when trying to get the same 2 achievements.

The easiest way to get these achievements is by facing the "Shrieker". You do not need to explore any dungeon in order to summon this monster.

Summoning the Shrieker:
The Shrieker appears during 3 different events. During one of these events, you have to lose 8 trinkets. So to summon him easily, go to any dungeon with any 4 recruits from the Stage Coach, equip them with 2 trinkets each and have them killed. The Shrieker will now appear as an additional mission in the "Weald". If one of the 8 lost trinkets is a very rare trinket, you will get a "Horrid Shrieker" (Champion Dungeon).
Do not worry, you will get your trinkets back after defeating it!

As you know, you do not have to kill the Shrieker to complete the mission. This is because on his last turn (in turn 4) he flies away, ending the battle.


Unlocking "Lone Survivor":
Only one hero should be used in the mission. My recommendation would be to use a Crusader, a Leper, a Man-at-Arms, or a Flagellant, as they are good tanks that can also buff themselves to further resist damage, or just dodge it. The Crusader, the Flagellant, and the Leper are also capable of healing. Make sure you equip good trinkets that increase dodge, HP, or PROT.
Focus on survival, during combat, rather than attacking!


Unlocking "Dysfunction":
Get 4 afflicted heroes beforehand. If you don't have any at the moment, you can always go to a dungeon and engage in combat and retreat until you have afflicted all 4 heroes (retreating from combat always increases stress). You should leave any afflicted heroes back in the village (don't use stress relief activities!) and explore a new dungeon and repeat the process if one or more heroes get virtue instead of affliction.

You can take any 4 heroes, but in my opinion:
One of your 4 heroes should be able to heal other teammates, the best would be a Vestal as she is the most reliable healer. If you are afraid of losing her, you can always take a Man-at-Arms and guard her, but it is not necessary.
I would also recommend that one of your heroes be a Jester: you are fighting with 4 afflicted heroes and the Shrieker has several abilities that can induce stress (not counting critical hits). His last move before fleeing deals 50 stress damage to all heroes.

As for the remaining 2 heroes, you can take anyone you want, but due to their affliction you should not risk much, so the best choice would be a Man-at-Arms: he can guard other teammates (and buff himself in the process) and with "Bolster" he can buff the entire group, increasing their evasion and reducing the incoming stress they receive. It would be optimal to take 2 of them, but if you are like me and do not like using the same class twice in the same group, a Crusader, Flagellant, or Leper would be the next best thing.

Now get on the road to the mission and make sure to manage their stress (and health). This shouldn't be too difficult!


Notes:

• If you are going for the "Lone Survivor" achievement and you are using a hero capable of stealth, do not rely on him to survive, since the Screamer's attacks ignore stealth.

Good luck!