I've been looking up a lot of discussion about these abilities, and everybody seems to be in consensus that you can use Kinetic Blade with iterative attacks with no problem. That's not what I got from my reading of it.
Here's the language that's confusing me:
Kinetic Blade: "You can use this form infusion once as part of an attack action, a charge action, or a full-attack action in order to make melee attacks with your kinetic blade." (Bold added.)
Kinetic Fist: "You can use this form infusion as part of an attack action, a charge action, or a full-attack action to add damage to each of your natural attacks and unarmed strikes until the beginning of your next turn." (Bold added.)
Why the difference? Does it mean that you can only use Blade once per round? Or does this mean that if you're spending burn on Blade you have to spend that burn for each attack, where with Fist you only spend it once? Is the difference in language just because Fist lasts until the beginning of your next turn? Or is this just weird, inconsistent writing?
I have a gut feeling that this has been cleared up in a discussion or errata somewhere, but I couldn't find anything. Any help would be appreciated.
The effects are very, very different, hence the different language.
Fist adds a damage bonus to each of your unarmed attacks, until the start of your next turn, but you also activate it only once.
Blade kinda turns your kinetic blade into a melee weapon until the end of your turn, with which you can full-attack for full blast damage on each attack, as written. The "once" just means you don't have to summon the blade on each of your individual attacks.