The most powerful of all the Titanian Eternals, Thanos, has a very difficult and unpleasant character. The Marvel villain is exceptionally arrogant and brutal to everyone around him. No mercy is shown to those who stand between him and the completion of his quest, whether it is the destruction of a world or the acquisition of a power source.
On the other hand, the Mad Titan is willing to work with more powerful superhuman beings in order to get what he wants and respects individuals with qualities that are reminiscent of his. The stories of DC Comics feature certain heroes, which Thanos is bound to hate and some others, which could easily become his potential allies under the right circumstances.
10 Hate: Superman
Thanos would want to kill Superman mainly because Kal-El preaches the exact opposite values - selflessness and protection of every single life of a sentient being.
Thanos would gladly destroy Earth and its population if that meant pleasing Death, but defeating Superman would be insanely difficult, provided of course that he is not in possession of the Infinity Gauntlet and all six Infinity Stones. Also, Clark would never be his ally. Their relationship could only involve a fight to the death.
9 Get Along With: Ozymandias
The DC hero, who Thanos would not only get along with but would wholeheartedly befriend (and maybe keep as a sidekick or a pet) is Ozymandias.
Largely considered to be an anti-hero for choosing to kill 3 million people in order to unite the Earth, Adrian Veidt is not afraid to sacrifice (others) to achieve larger goals just like the Mad Titan. If Veidt was part of the Marvel universe, Thanos would gladly proclaim him to be one of his Children, and in all likelihood, he would be his favorite.
8 Hate: Wonder Woman
Diana Prince believes in peace, and she will display untamed ferociousness in battle in order to achieve it. While her formidable fighting skills will undeniably earn Thanos' respect, Wonder Woman's superhuman abilities would also make the Marvel villain feel threatened.
He will likely despise her first and foremost for not using her talents of a warrior to achieve world domination. Diana has been innocent and commanding but never been cruel, so she would likely be Thanos' nightmare.
7 Get Along With: Dr. Mahattan
The relationship between Doctor Manhattan and Thanos would be quite intense. The "Indestructible Man" has abilities that Thanos can only challenge if he is at his full strength, so the Mad Titan would be compelled to be his ally.
Additionally, the boredom and carelessness that the former Jonathan Osterman felt for Earth are very much in line with the Thanos' own alienation to normal beings. These two are in possession of higher minds - they have grown beyond normal human interactions and can have long and thoughtful talks worthy of gods.
6 Hate: Martian Manhunter
When it comes down to the Martian Manhunter, Thanos' problem wouldn't be disrespecting the alien because of his innate kindness and absolute nobility; it would be J'ónn J'ónzz's desire to destroy the Mad Titan. The two powerful warriors' history would instantly make them foes.
The Martian is the last of his kind - his entire race was wiped out, and Thanos is famous for destroying planets' populations on a regular basis. If that's not enough, their personalities are different too. Thanos is a big talker, whereas the Manhunter is the silent type.
5 Get Along With: V
V and Thanos don't really have a lot in common. V is fighting for the common people, whereas Thanos (in most comic-book versions) is only killing for his own benefit.
That being said, V's path has transformed him into a terrorist, and he has delivered a fair share of destruction to society and world order, which would undoubtedly earn the Mad Titan's approval. Both characters are willing to cause massive damage in order to achieve their goals, and they would definitely have a thing or two to learn from each other.
4 Hate: Aquaman
Thanos would have little reason to get along with the King of Atlantis. There was a short period of time when Aquaman despised humanity, but experience and his good nature allowed him to overcome the negative emotions.
As the ruler of the underwater kingdom, he has become extremely wise - the embodiment of a true king, willing to devote most of his time to care for all living things in the ocean. Thanos lives to serve the needs of no one but himself, let alone a bunch of nautical inhabitants such as fish, octopuses, and such.
3 Get Along With: Doctor Fate
Hector Hall is a nice, caring, sympathetic guy when he is not wearing the enchanted helmet that transforms him into Doctor Fate. DC's most powerful sorcerer is someone who is more than willing to make sacrifices for the greater good (whatever that might be).
He's a big thinker, and such a personality would match that of Thanos. As a matter of fact, the Mad Titan has a history of allying himself with a superhero of similar cosmic and magical strengths - Adam Warlock.
2 Hate: Shazam
Apart from Shazam's diverse and difficult to oppose powers, another thing that would provoke Thanos' anger is Billy Batson's caring and optimistic personality. He is a highly moral individual and is willing to put his life on the line in order to do the right thing.
Adding salt to the wound, Billy is a lifelong fan of Superman. Furthermore, DC's Captain Marvel is extremely likable, and he is capable of winning people's affection at an instant, something that Thanos won't be able to do, even (and especially) if he conquers the entire universe.
1 Get Along With: Specter
Spectre will humble Thanos simply by being DC's most powerful character ever. However, in order to operate and put to good use his god-like abilities, he needs a human host. That makes him a perfect companion in the eyes of Thanos because it means that Spectre can't really be a threat to him.
Since both of these characters consider themselves divine individuals, they would find a lot of common ground, and admittedly, the mere thought of these two joining forces would give the Justice League and the Avengers powerful goosebumps.