Well, a submerged wizard (wizard template + 2 refinements) could easily have control +2, power +1, +3 offense power focus, +3 offense control focus, +1 focus specialization (to make the foci the smallest possible) and conviction/discipline of superb. That's +10 control/+9 power offense, +7 control/+6 power defense.
A submerged focused practitioner (spirit channeling + diabolism ritual +5 refinements) could have spirit offense +5 foci, spirit defense +2 foci. That's +10 control/power offense, +7 control/power defense.
A submerged necromancer (evocation, thaumaturgy, kemmlerian necromancy, 1 refinement) is downright terrifying. +2 spirit power, +1 spirit control, +1 necromancy control, +4 necromancy control focus plus necromancy bonuses. That means power 8, control 11 necromancy/psychomancy at the speed of evocation, complexity 5 necromantic/psychomantic rituals finished at a single exchange due to control 11. As long as they are smart and they stick to legal necromancy/psychomancy to avoid Lawbreakers, they are badass. Of course, they could pretty easily go off the deep end as NPCs. In that case, run for the hills; they're gonna have full Lawbreaker 1st, 3rd and 5th. That boosts them to power 8, control 14 meaning they kick serious ass.