Magic Duels

I just found an incredibly easy way to get this achievement. In Gideon's very first campaign mission against the Akroan guards you will start with about 40 cards each. Literally about 33 of the opponents cards are lands. Just keep playing your creatures and attacking with the ones you know will easily kill his creatures while keeping yours alive. You should literally never even take damage. Once you each have about 20 cards left get rid of any of his creatures that are left. He will draw nothing but Plains cards from this point on. Simply keep skipping turns until you have less than 5 cards left in your library then attack with all creatures at once to finish him off, he should have no creatures to block with and about 30 plains cards out. Make sure not to sacrifice your Oreskos Swiftclaws on the weaker 2/2 enemies, you will need them to take out his 0/3 blockers.

The entire process should take about 15 minutes, there is no way you can lose this duel, his strongest creature is only a 2/2 so you should have no trouble blocking anything he throws at you. Just be careful with what cards you choose to block with, don't mind sacrificing some Glory Seekers and Elite Vanguards to block, you should still have plenty of creatures.

Note* I actually had two flying creatures out as well so it would have been easy to just attack him with those for a couple turns before I finished him off to get the Air Superiority achievement as well.

Other note* It is also possible to get the 4 flying creature achievement with this method. Thank you to ScenemorriS

Easiest to do on the 2nd battle in Jace's storyline. It is replayable (though not for any extra gold). Your opponent will constantly try to mill you down to 0 cards. Best thing to do is lower his health significantly and control the creature game. You should be able to get it where you has near 1 health left and a few turns to go. You can wait on the attacks until he mills you below 5.

Make sure not to let him mill you fully though or you won't get a chance to attack.