Good Afternoon. Is there a way to stop Partially fulfilling Kit items? Thank you

You might look at the preferences for controlling commitments to see if something like only committing when fully in stock might work here. That's mostly a shot in the dark. You could use a workflow or script to hide the fulfill button unless all kit items are committed. That one will be a bit of a challenge, but I'm more confident in that solution. Alternatively, you could look at doing an assembly item and building it when it's in stock before fulfilling - but this has some extra transactional work to go with it.