Heart of the Swarm Campaign- Korhal Achievements: The Reckoning

Normal Difficulty:

The Reckoning (10): Win.

Swarm Guardian (10): Complete the mission without the Hyperion ever taking damage.  This is relatively simple- make sure you respond immediately each time that Arcturus sends an elite group against Jim's base, and it'll simply never get shot up.  There can be some issues if you happen to have your base under attack at the same time, or your assault force is strung out or stranded at the far end of the map by your pursuing an attack through a channel that doesn't pass Jim's base, but this really shouldn't be an issue most of the time.

Zerg Rush (10): Win in 25 minutes or less.  This is actually not that hard- it does require that you quickly build up an assault force at the start of the mission, but most attacking groups of considerable size (particularly when backed up by queens) are essentially self-sustaining and can then roll through the map in whatever pattern you like.  It's not even that hard to manage this while opening all three gates for your allies to send units through, though that's really an unnecessary distraction in this situation.  Just keep on a constant attack and you'll pull this achievement off, no problem.  Do keep an eye on your base, though.

Hard Difficulty:

Speed Bump (10): Destroy the Odin before Mengsk activates it.  This requires not so much tactical planning and arrangement as overwhelming force at overwhelming speed.  The only way you're going to manage this is cracking into the Terran bases in the Northeast corner of the map the very instant it is soonest possible, so you can smash the various mercenaries waiting to be sent out at you and Jim as well as the Odin itself.  Make sure you're thorough once you get your attacking troops into the area, as the Odin doesn't wait at the gates of the fortress itself, but rather just outside and to one side.  The real issue is having an attack force that is both powerful enough to reach the thing and durable enough to kill it while still taking attacks from the myriad other enemy units spawned by the Terran bases around it and each other.  You may also face some difficulty handling incoming enemy attacks on your own base at the same time, much like with the Zerg Rush achievement for Normal difficulty- it's up to you to determine how much value you're going to place on your main base and being able to replace your attacking forces as they get depleted by the hustle through enemy lines.