Despite Del's usual mocking of Rodney and occasional exploitation of him, he does often show himself willing to put his own neck out for his sake. The most notable occasion is in "Little Problems" where, given the choice to use some recently acquired money to keep his promise to help an engaged Rodney put together a deposit on a flat, and paying off his debt to the local gangsters, Del chooses the former (and takes a beating for it).
There's another, very subtle one earlier; when the Driscoll brothers catch up with Del in the pub, Mickey and Jevon run but Trigger stays, even daring to talk back to one of the thugs after they ordered him to leave, despite the fact that he, unlike Mickey and Jevon, had nothing to do with the situation. He only leaves after Del asks him to.
After Del's brief attempt at managing a band that Rodney was a member of goes horribly wrong in "It's Only Rock & Roll", Rodney yells abuse at Del for several straight minutes... then reveals that he's just quit the band, because they were saying even worse things about Del, and no matter what Rodney personally thinks of him, he wasn't prepared to have anyone else talk crap about Del. The moment is subverted in the next scene, when it's revealed that shortly after Rodney quit, the band secured a multi-million pound record deal, and are predicted to be the next big thing.
In "Strained Relations", after Del refuses to let Uncle Albert move in, Del and Rodney happen to meet up with him at the Nag's Head. Del unbends slightly and invites him for a curry. Rodney says they'll never get a table at this time of night, and Del says "You're right. We'll have to get a takeaway... and eat it at home."
Also in 'Strained Relations', Del's outburst after Rodney accuses him of getting over Grandad's death too quickly shows that although he often abused the old man, he really did love him:
Del: Get over it?! What a plonker you really are, Rodney. Get over it. I ain't even started yet! Ain't even started, bruv! And do you know why? Because I don't know how to! That's why I've survived all my life with a smile and a prayer! I'm Del Boy, ain't I? Good old Del Boy- he's got more bounce than Zebedee!"Here you are pal, what you drinking? Go on! Hello darling, you have one for luck!" That's me! That's Del Boy, innit? Nothing ever upsets Del Boy. I've always played the tough guy! I didn't want to, but I had to and I've played it for so long now, I don't know how to be anything else! I don't even know how to...
[Beat] ...oh, it don't matter. Bloody family! I've finished with them! What do they do to you, eh? They hold you back, drag you down, [On the verge of tears] and then they break your bloody heart!
Rodney: (whispers) I'm sorry.
In 'Hole In One', after learning about Albert's tendency to pretend to fall down holes to claim compensation, and the fact it's nearly got them in serious trouble with the law, Rodney and Del's anger at Albert for the furore thaws almost immediately when Albert reveals he did it to get money to help the financially troubled brothers, both to repay them for the kindness they'd shown in allowing him to stay with them, and to allow them to pay for Grandad's headstone.
Del: [awed] You did this for Granddad's headstone?
Uncle Albert: He was my older brother, Del. When I was a kid, he used to look after me. I never did anything for him, never had a chance to...until now.
One of Del and Rodney's final exchanges in "Sleepless in Peckham". After the matter of Rodney's real father is revealed, he asks Del if he is like his true father in any way. Del's response is one of the most poignant moments of the series.
Freddie the Frog was a professional burglar. He was disloyal to his friends. He was a womaniser, a homebreaker, a conman, a thief, a liar and a cheat. So no, Rodney. You are nothing like him."
The entire scene where Rodney finally comes to terms with Cassandra's miscarriage, but particularly The Reveal that Del intentionally sabotaged the lift's control to trap them inside, simply because he knew it was the only way to get his brother to open up.
In "May the Force Be With You", when Slater arrests the Trotters for possession of stolen microwaves and several trumped up charges, Del demonstrates that he's perfectly willing to be sent to prison, if it means that the charges will be dropped against Rodney and Grandad.
In "Who Wants to Be a Millionaire?", Jumbo Mills, an old friend of Del's returns from Australia and offers to bring Del out there to make it big. When Rodney's application for emigration is rejected, Del is left with the choice to go without him or give up his chance to fulfill his dream and stay. He opts for the latter, the episode closing with Del making out that it's no big deal, much to Rodney's joy. Del choking up as he sings the line "Who Wants to Be a Millionaire" tells us just how hard it was for him to give that opportunity up.
In "Thicker Than Water", when Reg Trotter badmouths Del and Rodney's mum, Del leaps up and tries to physically attack him before being restrained by Rodney and Granddad. Just goes to show how much Del loved his mother.
Del's absolute ecstasy at learning that he was to become a father.