I need to learn to be more humble.

Indifference to other living creatures, to the planet, to cruelty, to suffering, to injustice.

that very indifference.

Well defined by the story of the Good Samaritan.

In my own life , I like to consider the suffering of animals, as well as people, but I never feel like what I do is enough.

That is it is the hinge that all other sins swing. Some of the old lists would agree with you that humility is the opposite of pride.
pride - humility
avarice - charity
envy - kindness
wrath - patience
lust - chastity
gluttony - temperance
sloth/acedia - diligence

And I pretty much go along with that; Pride is setting yourself apart from and over others around you, as well as God - it's looking at other people as objects, things to be overcome or used.

Humility is a good trait - although there are forms of humility that seem like pride in different clothes. In other words, genuine humility doesn't draw attention to itself. Along with humility, genuine gratitude also helps tear down pride - acknowledging how others help us (as well as the blessings of God) helps us see our Pride for the sham it generally is.

Bryant

emanate from pride, including indifference mentioned above, sloth, lust, etc.
I believe Love is the greatest virtue; it may be called by other names as well - Charity, Kindness.

If we all just practiced simple human kindness.....

We all have it. Only one is unforgivable.