Casira, you've brilliantly identified the three main markers for measuring toxicity:

1.) PATTERN (is there one?)

2.) MAGNITUDE (what impact it has?)

3.) CONSCIOUSNESS (the offender's ability, or willingness, to self-correct)

Of course, there is still a certain level of subjectivity to this measurement. But you've provided us with a good barometer to keep from overusing the word/term.