Karma can be destroyed by not having a chance to happen in a specific
lifetime - for example in this lifetime or the next one - right ?
Yes. Only when karma has 0 (zero) chances to produce effects in the future (this lifetime, next, or the next, or the next, or ANY life in the future), it can be said that it's destroyed.
Karma can only be destroyed with attainment of Nibanna. Then, karma will not produce any effects.
If Nibanna is not attained, a potential will remain for karma to produce wholesome, unwholesome or neutral effects.
Unwholesome effects raise the potential for future effects. Wholesome effects lower the potential for future effects. Neutral effects neither raise nor lower the potential for future effects.
When karma is not destroyed, only its potential for future effects can be changed.
The potential of karma to produce effects in the future can be diminished to 0 only with attainment of Nirvana.
If Nirvana is not attained, the potential of karma to produce effects in the future will always be more than 0.
Please note that this does not mean that if one attains Nirvana or Nibanna, the potential for karma to produce effects is impossible to be more than 0. It can become more than 0 again, only it will come from wisdom, not ignorance.
Here it says:
Subsequently effective (upapajjavedanya) kamma is kamma which, if it
is to ripen, must yield its results in the existence immediately
following that in which it is performed; otherwise it becomes defunct.
Defunct (ahosi) kamma: This term does not designate a special class of
kamma, but applies to kamma that was due to ripen in either the
present existence or the next existence but did not meet conditions
conducive to its maturation. In the case of Arahants, all their
accumulated kamma from the past which was due to ripen in future lives
becomes defunct with their final passing away.
Above it does not say that defunct kamma means that it is destroyed. The way I see it above, the term 'defunct' is ambiguous - it could mean "the potential for future effects is exactly 0 (zero) (thus karma is destroyed)" or it could also mean "the potential for future effects is so small that there is almost 0 (zero) chance that it will produce effects in the future (thus karma is not destroyed)". I know it's the latter.
Here it says:
"Monks, I don't speak of the wiping out of intentional acts that have
been done & accumulated without [their results] having been
experienced, either in the here & now or in a further state hereafter.
Here it says:
"An action to be experienced cannot be turned, through striving &
exertion, into an action not to be experienced.
And here it says:
Here, following Norman (1997:166), I use the reading upapajjaṁ or
uppajjaṁ “in the next life” (rather than the variant uppajje).
Buddhaghosa “corrects” upapajjaṁ here and else where to be a
tatpurusha, as upapajje or uppajje. The Commentary explains this
sentence (wherever it occurs) as referring to “3 kinds of karma” (ti
kamma), according to the time of their ripening (vipāka) or fruiting
- karma experienced in the present life
- karma experienced in the following life
- karma experienced in a subsequent life
However useful such an idea may be, it should be noted that it is not
attested in the early Canon. Discourses such as the Deva, daha Sutta
(M 101) simply speak only of two kinds of karma in terms of time of
ripening or fruiting, that is:
- karma “to be experienced here and now,” and
- karma “to be experienced in another life”
Thus said, my position remains unchanged.