Kill the Butcher without being burned by floor fires or being grabbed by Ancient Spear on Hell difficulty or higher.
There are two things you need to avoid here. The Butcher’s playground is divided into 6-7 sections, and any of the sections can be on fire at any point, dealing a ridiculous amount of damage to you if you stand in it. Part of the achievement is to avoid this fire. The Butcher has several signature abilities as well. Ancient Spear involves pointing at a party member (or you, if you are playing solo) with his massive axe, and a split second later, sending out a hooked spear that pulls you to him. This is the other part of the achievement.
Once again, if you are an Inferno player, you can go back to Hell difficulty and get this achievement without any trouble. However, if you are a crazy purist, you can do this on Hell difficulty, as long as you have good reaction time and positioning.
The best thing you can do to avoid these is to stand at the border between two or more floor sections. This way, you will only need to move a teeny bit if one of them gets caught on fire. This strategy works even better if you have the choice of side stepping onto two sections instead of one. Other than that, always keep an eye on the floor. It takes 2 seconds for the floor fires to start hurting, and that is plenty of time for you to get your butt to safety.
This ability can be avoided in two, and possibly a third, untested way.
First, you can outrange it, so Demon Hunters can stand a full screen’s length away and even if the spear is hurled right at them, they will avoid it.
Second, you can sidestep. The Butcher points to the spot where he will throw the spear, and regardless of how the player is moving, once he has pointed (unless interrupted) he will toss the spear in that direction only. All you need to do it simply move 2-5 feet prependicular to the path of the Ancient Spear. If you are smart, you will position so that this movement moves you along the boundary between floor panels to avoid teh floor fires.
The third, and as yet untested method is to use a class ability. As a Witch Doctor, if The Butcher points at me, I activate Spirit Walk a second later. The hurled spear harmlessly passes through my spirit state and I bypass the mechanic entirely. However, from an achievement viewpoint, I am not sure if this counts as “not being grabbed by the Ancient Spear”.
All in all, this is a fairly easy achievement, and the only reason you will need multiple attempts is RNG if you are only geared for Hell difficulty.
Pro Tip for Melee
If you can take a beating, avoid the Butcher until his first charge. Have him charge into the entrance wall. Then stand there (effectively avoiding floor fires) and tank him (effectively avoiding Ancient Spear) and take him out! Just watch for his big swing and charge.
Have the Skeleton King kill 15 of his own Forgotten skeletons before killing him.
The Skeleton King has a few abilities, but the one you need is his whirlwind melee attack. It creates a circular blue effect around the Skeleton King, so it’s kind of hard to miss. This ability can also hit his minions, and you need him to kill 15 minions in the same kill run to get this achievement.
The strategy can vary depending on which route you take.
If you decide to do it on normal as you are leveling (you should be around level 7-9), then it will be a hectic fight. Remember, you don’t need the 15 minions dead in the same whirlwind attack. He can kill a few at a time and you will still get the achievement as long as they add up to 15 over the course of a single kill. I would suggest kill a few skeletons yourself because they drop health globes which you will need to stay alive, and generally steer clear of The Skeleton King. There is no reason for you to soak his damage. When you are ready to have the adds killed, position yourself between the minions and The Skeleton King. He will either move or teleport over to you, and you can then move out of the way when he starts whirlwind.
The easier way is to get to a higher difficulty level. My Witch Doctor is on Act II Inferno. I can just stand at The Skeleton King, and without so much as moving, I can get the achievement. This is because the spawned enemies and The Skeleton King will stack up on you, they won’t be able to hurt you, and every time The Skeleton King swings, he will continue to kill his own minions. However, you should be careful about thorns though, as thorns will essentially kill everything that hits you.