Kind
The word "altruism" would never be associated to the Varia. Ruthless, cunning and cold-hearted assassins, the very motive driving them is their self-profit. However, "kind"? "Kind" was a word that was used to describe them on occasion by the Vongola Decimo's famiglia.
Most notably, Lussuria would be at the forefront of such a visualisation of the kindness the group could offer. His healing capabilities seen as a balm to hurts for the Sawada's brat group. But seen with a much more practical and jaded light from Varia , as survival and mending not for the better but for the fight in Varia. This was his kindness to his associates. On a darker tone, he could kill as well, crippling his opponents with the flame of rejuvenation was not merciful at all. It was prolonged agony. Levi was also known as caring when one observes his behaviour with Xanxus, his mother-henning behaviour a glaring abnormality in a world of conniving and murdering spies and assassins.
On the opposite spectrum, there was Mammon. Money and deals were his daily transactions, harsh and forgiving, the failure of aligning to his terms will result in imminent death. His propensity to give out deals even to the weak was a form of kindness. Strength is earned, true enough and a practice adopted through the whole mafia. However, without a chance, the strength would not be able to be developed. He had the ability to annihilate many but chose to do so only after his seemingly cruel and mocking deals. If the opponent was worthy, this was a viable lifeline, if not he deserved it. Perhaps he was just bored , or whimsical but being such a stickler for maximising his profit even in the most minute amounts, was a form of kindness to those who understood true strength.
Then there came Belphegor, honestly a maniac and his kindness comes from his apathy towards anything that bores him. Of course there were occasional bouts of his insanity but there were many out of his radar and they should be thankful for it. Fran being the subject of his "cruel" torture was another form of apathy, truly the epitome of the word. He was unaffected by most if not all, including the weird Varia moments which is can be said to be out of the world, given their average sanity ratings. Matching with each other, they had weird interests at odd times, often prioritising their pleasure over their mission. This unexpected turn of events often resulted in the enemies unintended survival.
Squalo, the naive Yamamoto would definitely argue to be kind, with his weirdly blunt and paradoxical ideals. Claiming Squalo to be his teacher, was only one of his misnomers he had of Squalo, known as the Emperor Sword and the right-hand man of Xanxus. However, Squalo actually did have a soft spot for idiots such as Yamamoto. His passion for swordsmanship is his strength and weakness in his tendency to challenge with more restraint on using "unhonorable" methods that were the life of an assassin.
And finally, Xanxus. He often destroyed the infrastructure of Varia, having the reputation of irritable and untouchable. His unreasonable tantrums and his harsh death threats against subordinates who did not meet his expectations a telltale warning to cower in fear at the mere mention of his name. However, in his brusque and also blunt manner, Xanxus has demonstrated the most practical form of care in the assassination world. His kindness was demonstrated in his harsh and taciturn words. In his harrowing and rather tragic backstory, he was subjected to much worse attitudes and also treatment, in which he realised the value of hardship in honing oneself while acknowledging the fact that going overboard was detrimental. His constant dangerous and unpredictable behaviour helped place his subordinates high on the food chain, either having the ability to avoid the dangers with a keen senses or the uncanny ability to placate such a situation. His treatment of them became a favour in nurturing them to become workers of higher efficiency and most importantly higher rates of survival.
Kindness need not be done in kind gestures, and superficial and idealistic gestures could lead to the demise of the person intended instead. Especially in the world they lived, survived and worked in.