The easiest way to make the worst possible meal is to make kibble out of human meat. This way whoever eats it gets the -15 human meat mood debuff and the -15 ate kibble debuff. If you can be arsed to do a not worthwhile amount of micromanaging, you can make human meat + insect meat kibble to make it even worse.

I guess if you really wanted the min/max the meal debuffs, you could make separate stacks of kibble, one for each "bad" food ingredient. Set up a kibble buffet and lock the victim in a room until they've sampled one of everything from the poop kibble buffet. I've had at least a combined -75 mood from stacking bad food mood debuffs before.