Yeah that ~45 hour achievement took a lot out of me. Boring, time consuming, nerve wracking... I need to update my achievement case for the "never again" achievement with that one lol. And yeah my hands would go numb and I'd stop and come back. And repeat it all over again.
Ionball isn't all that bad. Later in the game you can get upgrades and that helps a lot. Do the million points in a second play through. Once you get the hang of it it's not so bad.
Tier 3 is easy just very time consuming. Angry Birds Space has an achievement for breaking 500k blocks which is ~45 hour grind after you get all the other achievements. I think Corrupt is close to getting Tier 3 also.