All you have to do is max out any particular stat--lets say, Cleverness--and choose the correct dialogue options.

For Cleverness, Honesty, and Respect, choose "... words and thoughts" when you first start off.
For Bravery, Ferocity, and Kindness, choose "...actions and attitudes."

You'll need to remember what you choose now for later:

"... fighting, and eating, and screaming!" is Ferocity

"... standing unafraid against frightening enemies!" is Bravery

"... defending the innocent from those who would do them harm!" and "... helping the sick and soothing the woeful!" are Kindness

"... outsmarting everyone else!" is Cleverness

"... speaking true when others lie!" is Honesty

*At the end of your stint as an adolescent, the game will let you know what your highest stat is.

Moving smartly on. Once it comes time to Dissolve, all you need to do is choose to "embrace your fate">"go with them to Dissolve or become an Elder">"Dissolve. Become one with the Spawning Vat."

Important: You'll need to choose whatever you chose in the beginning. i.e If you first chose "... words and thoughts," you need to choose "Remember the ideas and thoughts that were dear to you" now--and vice versa. Then, you'll need to pick the stat you maxed (see the above selection explanations). Ta dah! You have a new achievement.

Rinse, wash, repeat for each of the stats.

**Dissolve into Mediocrity requires you to have low (<40%) stats before you Dissolve. Easy.

Just do all of the above. When it comes time to Dissolve, however, choose to "Embrace your Fate.">"Ask them to come back later.">"Slip away while nobody's watching.">"Go, go, go! Get away from Omen!" After that point, you can click whatever you want (the option that matches your highest stat, preferably) until the achievement pops up.

There are alternative ways, of course, but this is just the way I did it first.

This one's easy. Simply play through as you normally would and be sure that you Ascend.

You'll need:
High (>50) respect--Gained during adolescense.
Low (red icon background) Monsters View Humans--The Politick actions effect this.
Any Humans View Monsters--The Journey to Carmen actions effect this.
High Cleverness (just try and get as much of the stat as you can.

Then, simply choose "we can fight them!" when you are given the option to fight or flee. Then, choose to "use brilliant tactics." After a few more sections, you'll be presented with the option to kill all humans or not. Choose to kill them all and, bam, you have your achievement.

Once again, play through as you normally would and be sure that you Ascend.
You'll need:
High (>50) respect--Gained during adolescense.
Low (red icon background) Monsters View Humans--The Politick actions effect this.
Low (red icon background) Humans View Monsters--The Journey to Carmen actions effect this.
High Cleverness (just try and get as much of the stat as you can.

Near the end of the game, simply choose "we can fight them!" when you are given the option to fight or flee. After a few more selections, it will give you the option to surrender your army to the humans. Choose it and the achievement should pop up.

For this one, just make sure you have low respect, medium to high (>50) Monster View of Humans (effected by Politick events) and low (<40) Human View of Monsters (effected by Journey to Carmen events) . You basically want monsters to like humans and humans to hate monsters. When the humans come to attack, tell them to run. Due to your low respect, they'll ignore you and go to battle.

They fight and die, you flee and live. And you even get a spiffy new achievement!

Alternatively, Bladesinger suggests: Alternate way to achieve Monster Annihilation: high respect, low cleverness, low humans/monster, low monsters/humans, tell them to fight, due to your high respect they obey. Use clever tactics, fail the dice roll. I had low cleverness so I failed the dice roll, ending with all monsters dead. :)

You know the drill. Play through like you normally do--just make sure you Ascend.

You'll need:
High (>50) respect--Gained during adolescense.
Low Monsters View Humans--The Politick actions effect this.
and/or
Low Humans View Monsters--The Journey to Carmen actions effect this.

Near the end of the game, simply choose to flee rather than fight and you're done. Easy peasy.

You'll need
Low (>40) Monster View of Humans
Low (>40) Human View of Monsters and high (>40) respect.

When it comes time to fight, fight. Then, utilize clever tactics. It will ask whether or not you want to kill every human. Choose not to (the second option) and you'll have your achievement.

Easiest achievement in the game, really. Just make everyone (both humans and monsters) love each other. The dialogue options are pretty clear cut, so I won't go into too much detail here. In fact, if you did a playthrough or two, you should already have this.

If you still need help, drop a comment below. Thanks for reading!