>>44441577+6 aqua jet actually doesn't OHKO a defensive defog corviknight, but it's very close to it (82-97%). It doesn't matter because there's absolutely nothing corviknight can do to revenge kill a water type with 100-100-100 bulk, and if it's a slow corv azu is faster and simply clicks knock off instead.
Now mandibuzz, that's an interesting one. Defensive doesn't die to +6 aqua jet either, but azumarill's attack is so high mandi actually has a shot to OHKO with foul play, and since azu will always be at 75% or lower after belly drum, foul play is a guaranteed kill on it.
None of this matters since an azumarill with those stats would be ubers anyways.