hmmm for SAKI to do it, I suppose that if she actually tries to come on to him and not in that teasing, just from a distance way, then he will erupt. In canon he gets angry when he sees Lenalee sleeping on Allen's bed only because her skirt is like bunched up around her thighs -- so Saki doing something like that would incite a bigger response. That is, unless you mean meltdown in the complete breaking down kind of way -- and that's harder to say...maybe if she actually mocks his faith in God...