Is there a cyp450 inducer stronger than st john's wort?

Depends: There are many subtypes of cyp, and each can be induced by different things. Induction is not always beneficial, as too fast phase 1 detox can produce toxic metabolites faster than phase 2 detox can get rid of them.

Depends: It all depends on the amount you take; some antibiotics and antiseizure medications are very strong cyp450 inducers. That being said, it's hard to quantify against "st john's wort" because there is no regulation on the presence of active ingredient in that product.