Luciano Karosas, is a 21-year-old man based out of Argentina. He adopted a doggo-- Thanos who was suffering from a terminal tumor so that it could live the rest of his days to the fullest with unconditional love. 

Source: The Animal Rescue Site Blog

With a cancerous tumour growing inside his head, Thanos was living his last few days in an animal shelter, after getting abandoned by four families, before Luciano fell in love with him. 

Source: Unilad

Without thinking twice Luciano adopted him. Initially, he didn't want to give up on Thanos' condition and went to various vets with the hope to save Thanos's life. He further reveals:  

I found it hard to adapt to the idea of ​​how little time we will spend together. I took him to a stem cell veterinarian to see what we could do, looking for a little more hope (which had given him 40 days to live) and told me that there is no treatment that extends that time. 
Source: Diply

Unfortunately, he didn't receive a positive response from the vets. But Luciano didn't give up, he made it his life's main aim to make Thanos' last few days memorable.  

Thanos was happier than ever in the short time he stayed with his new master. He was pampered by Luciano and they both played and snuggled like any other healthy doggo, before he passed away. 

After all that Thanos had been through, being abandoned by various families and the tumour, he was finally happy and felt loved before he succumbed to his illness. He passed away knowing that he was a good boi who was loved.