TL;DR: Humanity evolved to cooperate, but also to compete - that's the rub

We are broadly altruistic creatures, because altruism serves us so well! Without cooperation, we would not have been able to defend ourselves against all the glorious megafauna of the African plains when we first climbed down from our trees, nor would we have known to cooperate around hunting, raising kids, etc...

It goes against our deepest natures to cause each other harm gratuitously (see Lasana Harris' work on dehumanisation), but we have developed all sorts of complicated systems to help justify it when it does serve our purposes - like taking over other people's lands or wealth... Then we use that 'kindness' (our unrivalled capacity for cooperation) to inflict maximum damage.

Humans are social creatures that have evolved to work together to survive.
Put them in a crisis and watch them work together. Put them in a time or relative prosperity and they'll stab each other in the back.

TL;DR - If viewed from a really, really distant point, I think humanity is overall kind.

• Taking a very, very broad overview of this--I think humans could be said to be kind overall. I think when we strip away all context (which, of course, is not ever possible, but let's just say we can for a moment), humans ultimately want to feel meaningful, experience ego-centricity, or at the very least go after pleasure. The conclusion we seem to come to eventually is that the best way to achieve all these things combined is--corny as it may seem--love. Either love, or a parallel embarking on a long-term journey of caring for and making the lives of humanity in total better, both of which require a large-scale development and employment of kindness. We achieve a sense of meaning, a soothing for our ego, and even a pleasure from the act of engaging in either of those ultimately kindness-based things.

• Searching for a sense of meaning could be viewed as not quite a "kindness-based" endeavor. I still think that it can be viewed as that, though, when looked at from far enough away: The quest for a personal sense of meaning usually has to be diluted into (perhaps "expanded outwards towards" is the better phrase) a search for larger humanity's sense or senses of meaning, as the pure egotistical being cannot outlast the relentless pursuit of something basically infinite against its finite self.

• I have a feeling this opinion is too unpopular, too catchall, and makes too universal a claim to stand any kind of test of time. But part of me thinks it might be possible that this overarching lens explains a lot of what's happening in our world, or at least what the majority of people are pushing for. Or will push for, Godspeed.

We all strive to be kind, but ambition often leaves kindness trampled to the ground in its wake.

• When people are shown a video of someone falling down some stairs, they laugh. At some point in your life, you will most probably have laughed at someone falling or slipping over. Humanities most common emotion is not kindness, and it never will be.
• Humanity seems to be ambitious more than anything else. This is the one trait that is highlighted continuously throughout history. People always strive for the best and to improve themselves. We compete with others, to do this, you sometimes have to shove others to the side. You cannot be ambitious and be kind.
• We all strive to be kind. However, it is not easy to always be kind. Instead, it is easier to fall back on selfishness and rudeness. Humanity can be lazy, and due to this, we are not kind overall.

Humanity overall is kind. Most people naturally are kind and caring but as they grow up are often swayed by systems of capitalism and the related corruption

• Most Children are naturally kind and much more understanding than adults, any arguments, fights etc... are not done in spite or to be consciously unkind it is just because they don't fully understand.
• Unkindness is learnt and taught by society and adults to children, with the system of Capitalism teaching people to put profit and material gain above other people
• In most case there is more good and kindness but bad things often get more media time and are often perpetuated by people with more power therefore can have more impactful consequences

We slaughter 70 billion animals a year for snacks we do not even need.

We start wars over religions that we do not even know to be true.

The sickest most vile acts ever committed have ALL been caused by humans.

Anything kind humans have done, they have only done for their own benefit.

Sorry for the negativity, but I think anybody who thinks humanity is inherently kind is viewing it from rose tinted glasses. I am not saying it is necessarily our fault, but humans are horrible.

TLDR: Humanity's inhumanity is limitless if you consider who humanity stands in relation to. Under strong social pressure we do unspeakable evil. Our desire to fit in might be our ultimate detriment, in fact

Humanity is fundamentally unkind (to say the least) to those we share the world with. To base the assesment on how humans treat the ones who are already socially conditioned to recognize as valuable, is as fallacious as saying "racist white people are kind because they treat other white people kindly!"
Yes, of cource we generally are kind to those we are taught have value, but what about all those others we are conditioned to see as worthless?

Despite our capacity to reason, be compassionate and moral, we are extremely weak to social pressures and personal enrichment. No other animal, being able to reason and empathize, have ever enslaved, raped, tortured and/or killed members of other groups, while rationalizing it as "natural", "normal" and "neccecary". But humans, despite being perfectly capable of seeing why those reasons are unjustified logically, continue to enslave, trap, exploit, torture, burn, cut, gass and kill billions of other sensitive individuals, by choice. Trillions of lives a year are violently taken for no justified reason.
And in addition, humanity is actively killing itself by killing all those defenceless animals. It's the main cause of climate destruction, global warming, lifestyle disease, pandemics and much more. The equation goes as follows:
Our willingness to disregard other groups emotions + our desire to exploit them for trivial pursuits + social pressure = a powerful coctail of ideological (self)destruction and evil.

The inhumanity of humanity is limitless. The condition we force animals to endure for our snacks and social comfort literally is limitless, and I'm never ceased to be amazed by the depravity and inconsideration we have inflicted, and continue to inflict, on "the other". Evil requires that one chooses to do harm while understanding it to be harm, and being able to avoid it. That is exactly what humanity does to those we share the world with.
And the main reason? Ideology and social pressure. There is massive social pressure to conform to unjust oppression. In the past of women and other races, today of animals.