Bubblebrain is of course a fool. He left the soul fragment in Harrys' forehead on purpose! He was just too stupid, lazy and arrogant not to. After all, he was the man with the plan. Now as for Tonks, she has no idea what she's in for. The same could be said for Bubblebrain. He seems to think that he can manipulate Harry into doing things his way and staying in England after he kills Tommy-boy. The old fool is playing with a thermonuclear bomb without realizing it. Say in the two to three hundred megaton range?