How does the story "One Thousand Dollars" by O. Henry show that disreputable people are also capable of compassion?

Love often changes a man, and in O. Henry's "One Thousand Dollars," the prodigal Robert Gillian demonstrates generosity and compassion alike.

After Lawyer Tolman instructs Gillian that he has received one thousand dollars from his guardian and uncle, who has recently died, Gillian opines, "It's such a confoundedly awkward amount" because he must spend this money and then give an accounting of it.

Gillian hurries to the men's club that he frequents to seek the advice of the curmudgeon called Old Bryson. With feigned disinterest, Bryson suggests that Gillian purchase something for the actress whom Gillian likes. But, when he goes to her, in her greed for more she rebuffs his offer. So, Gillian goes outside and asks the cab driver and a blind man what they would do with $1,000.00. But, their answers do not satisfy the young man.

Then an idea comes to Bobby Gillian. He has the cab driver take him back to the law firm of Tolman & Sharp, where he inquires if Miss Hayden were left anything in his uncle's will besides a ring and $10. "Nothing," Mr. Tolman informs him. Upon hearing this, Gillian's soul is renewed. He returns to his uncle's house and informs Miss Hayden that he is delivering to her a thousand dollars that old Mr. Gillian willed to her. Then, he declares his love for her, but she tells him that she is sorry. Even though she rebuffs him, Gillian allows her to keep the money.

So, Gillian heads to Tolman & Sharp to hand in his accounting for the $1,000, which he has given to Miss Hayden. When he does so, Tolman reads from the will,

In the event that your disposition of the $1,000 demonstrates that you possess any of the qualifications that deserve reward, much benefit will accrue to you....If you are prudent, wise, or unselfish, it is in our power to hand you over bonds to the value of $50,000, which have been placed in our hands for that purpose.

However, there is another stipulation. If Gillian has squandered the money, as he has done in the past..."in reprehensible dissipation," the $50,000,00 is to be paid to Miriam Hayden, ward of the late Mr. Gillian without delay.

When he hears this, Gillian tears up the envelope, saying, "It's all right....There isn't a bit of need to bother you with this....I lost the thousand dollars on the races. Good-day to you, gentlemen." 

It is with a light heart that Gillian walks out, whistling as he waits for the elevator because he is, indeed, reformed.