Board Thread:Questions and Answers/@comment-28340828-20180616205329/@comment-24900075-20180617012321

Tier 0 means they never had a weakness ever and was always, forever omnipotent. The very fact that they were High 1-A at one point means they aren't tier 0, period. A tier 0 is always tier 0 no matter what. You can't power up to Tier 0.