Hannibal viewers love to talk about the romantic relationship between Dr. Lecter and Will Graham, despite the former's many murder attempts on the latter. Granted, when being a serial killer who eats people is one's defining feature, it makes sense that person wouldn't have the healthiest way of showing affection. Still, it's clear that Hannibal does have deep feelings for Will, and that those feelings are reciprocated by the end of the series, but whether what they have can truly be called love is another argument entirely.
Hannibal creator Bryan Fuller hasn't been shy about the fact Hannibal and Will's bond is deeper than friendship, and that their story could be called a love story - albeit a very twisted one. Some people might argue that doesn't make sense, but going back to the early episodes, Dr. Hannibal Lecter and Will always had a spark in their interactions, and the pair found each other's company pleasant. The two men also found conversation with the other fascinating and saw each other as being on a similar intellectual footing.
So attractive is Will to Hannibal and vice versa that even after Dr. Lecter made multiple attempts on Will's life, and the latter also made repeated attempts to bring Hannibal to justice, the duo ends up together at the very end. It's almost like they were playing a dangerous, but exciting game, always hoping the other wouldn't truly lose. At the same time though, Hannibal sure came close to putting Will six feet under, so it was a game with decidedly high stakes.
Hannibal's first time almost killing Will was arguably not a murder attempt, but it very well could've ended Will's life, and the good doctor seemed unconcerned about that prospect. Partway through season 1, Hannibal takes a mentally deteriorating Will to see a neurologist and discovers Will's brain is being ravaged by encephalitis. He succeeds in keeping this from Graham, eager to observe and see where his condition ultimately takes him. Once Will finally figures out Hannibal was the killer he was searching for, Hannibal has succeeded in using Will's medical condition to frame him for Dr. Lecter's own crimes.
In season 2, Hannibal actually tried to kill Will twice, although it could be argued he was hoping Graham would survive, as he seemed to be grooming Will to kill by his side. The first, in Hannibal's "Shiizakana", was retaliatory to an extent, as an imprisoned Will sent a murderous orderly named Matthew to try and kill his nemesis, and when that failed thanks to Jack Crawford's interference, Hannibal then sent a former patient named Randall Tier to try and kill Will. The latter proved victorious, and he and Hannibal agreed to come to a truce at that point. However, when Hannibal eventually found out Will was secretly working with Jack to try and catch him, Dr. Lecter stabbed Will and left him to bleed out on the floor at the end of "Mizumono", while also killing Abigail Hobbs in the process.
By season 3, Hannibal fled to Italy but is of course eventually tracked down by Will and Jack. Hannibal looks to inflict some particularly horrific vengeance on Will in "Dolce," drugging and restraining him, then proceeding to begin cutting his head open with a cranial saw in a manner akin to Paul Krendler in 2001's Hannibal movie. Thankfully for Will, Mason Verger's thugs broke in and kidnapped both men before the "procedure" could be finished. Later that season, Hannibal has been locked up for several years, but he and Will reunite to stop Francis Dolarhyde. The pair end up killing him together in "The Wrath of the Lamb", solidifying their union, despite Hannibal having sent Dolarhyde to kill Will's family.