Some verses (page 216) from Nagarjuna's Treatise on Ten Bodhisattva Grounds on karmic offenses vs merit (good karma):
When a pint of salt is thrown into an immense pond,
its flavor remains no different,
However, if one instead mixes it into a small container of water,
the harshness of the salt makes the water undrinkable.
This is analogous to there being a person with a great stock of merit
who has but few karmic offenses
and who is not bound to fall into the wretched destinies,
but rather undergoes mild retribution under other conditions
while there is another person with only a scant amount of merit
who has committed but few karmic offenses that,
because his mental resolve is but narrow and small,
is caused by those karmic offenses to fall into the wretched destinies.
If someone’s physical vitality (lit. “fire”) is weak in its strength,
when he eats but a little of something difficult to digest,
although this person doesn’t die,
his body undergoes much suffering.
If someone’s physical vitality is strong,
when he eats but a little of something difficult to digest,
such a person never dies from it
and undergoes only a minor amount of suffering.
If the vitality of one’s goodness, merit, and wisdom is weak,
and he has committed but few bad karmic offenses,
there is nothing to save him from these karmic offenses,
and hence they are able to cause his descent into the hells.
In the case of someone possessed of great merit,
even though he may have done bad things involving karmic offenses,
they may not compel him to fall into the hells,
for he may instead undergo only mild present-life retribution.
Take for example the case of Aṅgulimāla.
Although he murdered many people
and also wished to harm his mother and the Buddha,
he still attained the path of arhatship.