"You Shall Not Pass" and "My Precious!" Achievements

I've been trying to get the "My Precious!" achievement for days, but to no avail. I usually get a Reactor on my Starport and Tech Lab on my Barracks at the start of the mission, then use my starting Vikings along with the few Reapers I can pump out to destroy the first Nexus. Unfortunately I can only get about 5 Reapers and 7 Vikings out at this point, and by the time I've just started watching all my Reapers get roasted by the Colossus guarding the second Nexus, the Purifier has already destroyed the first settlement and his well on his way to the second.

I've been restarting the mission dozens of times, trying to do this same strategy as fast as I possibly can, but it's obviously not gonna work. What can I do to get this achievement? (and by extension, the "You Shall Not Pass" achievement?)

 

So what, nobody knows how to get the "My Precious!" achievement?

/bump

 

I think I used pure vikings with upgrades on that mission, was not that hard...
And you can do "You shall not pass" on Normal, will be a lot easier imo

 

Don't make any reapers. Just make lots and lots and lots of vikings, with a few marines and marauders to defend your base, and ship upgrades of course.

The first nexus (just to the east of your base) can be destroyed with just your initial three vikings. Fly over there, destroy all the phoenixes and phase prisms, then land on the high ground and you will have just enough range to shoot and destroy the nexus. Be sure to repair any weak vikings you have after the nexus is down.

Then you can do the same thing for the second nexus. Approach from the northwest over the high ground, destroying every air unit you see, and land one viking to the attract the attention of the colossus so all your flying vikings can destroy it. Then you can land all vikings on the high ground and shoot the nexus.

The final nexus is rather difficult as there is no high ground, so you better have about 14+ vikings at this point. Once again, approach from the northwest and destroy any air units you see, then just land on the point of land over there and battle it out with the archons that come to fight you. On hard there is also a high templar there that will storm you, so be sure to dodge that and take him out. Then you can destroy the nexus without a problem.

Finally, to take on the purifier, you should have 20+ vikings. Do NOT attack it with one big clump of vikings though, because it will use vortex on all of them. Instead, just send one or two vikings forward, and it will vortex those while you attack with the rest from a different direction. Another thing is always stay away from the purifier, you can safely attack it out of it's range, although you do have to deal with the carriers and stalkers it summons. But after you do, just attack it with everything and it will go down quick.