Wade dies and immediately comes back to life.

The moment you try to write his name on the death note, it burst into flames and burns your hands

wade have the plot armor for this and light will be piss that he not die

Deadpool would break the fourth wall then go fuck up Light after he has a continuous heart attack trying to kill him, let's be honest. Ryuk would be interested as hell as to why Deadpool isn't dying from it, and if Deadpool gets the Death Note he'd definitely get followed around by Ryuk... And be pissed it isn't Death doing so instead.

It technically works, but it can't keep him dead. Since the Death Note would believe that Deadpool is dead after one use; Light wouldn't be able to use it on him again. And if you think that 616 Wade hasn't survived crazy stuff, he once got turned to ash by Thor, punched to mush by Hulk and he survived a Nuke at the Epicenter.

In thinking wade would be having a heart attack while the healing factor does its work almost like a permanent heart attack constantly killing him

Or what happens if he jumps into a vat of molten iron , like when it freezes

He will write that he walked down the street into the crematorium and climbed into the working

Can someone be clinically dead via Death Note heart attack and still be revived? Like if the victim was at a hospital with all the needed staff and medical equipment nearby?

"Wade Wilson dies from tripping and falling on his own Muramasa blade"

Can the Death Note cure his cancer? Wink wink.

The death caused by the note is not a permanent death that prevents resurrection. In the pilot, there is something called the death eraser, which can bring back to life the person killed by the death note.

And Deadpool could look outside the story itself to find loopholes and making it meta. Like going online to find arguments himself to outsmart reuk like bugs bunny

Alternative, have him encase himself in cement or something to die of suffocation. He isn't super strong and lack of oxygen keeps killing him basically instantly.

Most of the effect from what I recall is happened by Ryuk power manipulating the event.
So the Deadnote is just an supernatural hit list.

Deadpool would goes to Strange to figure this out what been supernaturally happening to him.

also thing is, deadpool brain isn't required for his regeneration to work, it just automatic cells regeneration so that's a factor problem too

Unstoppable force vs Immovable object

Alright you did deadpool. But what about someone who negates the rule of death, Andy from Undead Unluck. There is multiple factors to this actually.
Andy isn't actually who he was orginally. He's the spilt personality of Victor, the orginal Undead, who got a magical artifact stuck in his head which suppressed Victor and birthed Andy. Andy was the name given to him by Fuuko when she met him and found that Andy had no name.

Considering the movie Deadpool is being used, the closest comparison could be Cassandra Nova from the Deadpool and Wolverine movie.

Wade would heal any after death. His healing factor is metaphysical iirc, his soul literally cannot be taken by death. So as long as his abilities are present he cannot die permanently. Wade would require an inhibitor or leech's powers. That being said considering how shinigami work, what woukd happen if a shinigame wrote wades name down? They gain his life? They gain his healing factor?