If you view the achievements screen and then drag the screen around to try and find the achievements that don't exist, the game crashes:

java.lang.IllegalArgumentException: bound must be positive
at java.util.Random.nextInt(Random.java:388)
at net.minecraft.client.gui.achievement.GuiAchievements.func_146552_b(GuiAchievements.java:311)
at net.minecraft.client.gui.achievement.GuiAchievements.func_73863_a(GuiAchievements.java:204)
at net.minecraftforge.client.ForgeHooksClient.drawScreen(ForgeHooksClient.java:355)
at net.minecraft.client.renderer.EntityRenderer.func_181560_a(EntityRenderer.java:1095)
at net.minecraft.client.Minecraft.func_71411_J(Minecraft.java:1077)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:369)
at net.minecraft.client.main.Main.main(SourceFile:124)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

There is an rftools achievement page. I don't know why but there is.

Also, the newest version for 1.9.4

I will check it out

What version of RFTools? And how is this even related to RFTools?

I mean I don't do achievements in RFTools for 1.9.4 yet. So I don't see how this can be caused by rftools?

Just put one achievement on the page or remove the page for now

I'm fixing the achievements like how they were in 1.7.10. Will be in next release