Just to let you know this is entirely my opinion mixed along with a little bit of facts. Please comment ot let me know what you think and the rankings are in no specific order, its just the top five. (Diamonds do not count)
1: Lapis Lazuli
Previous regeneration Lapis
Ok, I really just love lapis so this might be just my fondness for her but I think Lapis is actually super powerful then she already appears to be. One reason is because we've never actually seen her gem weapon. People have never really thought of this but I will argue that her wings aren't really her gem weapon. A fact to aid this is that her gem doesn't glow when she pulls out her wings, like all the other gems. (Except that one time when Steven litterally just healed her cracked gem, so they added the glowing gem for a little pa-zazz.) For another thing, she can control water. No other known gem is known to have a power anywhere near this.
Just healed Lapis.
One more reason why Lapis might be one of the most powerful is the fact that she was able to hold jasper down so long in the form of Malachite, and she also had the power to use her talent of water manipulation to keep Jasper down.
.png){kind=link}