String 1
Deadpool’s most basic attack string that works on the whole cast on hit or block is
c.:l: s.
c.:h:
on hit, do :s:
on block, you have options.
You can do :d: :df: :f: +:m: or :d: :df: :f: +:l: :l: . If you choose pineapple surprise and it hits, you can combo with a dash :s:.
String 2
This is a slight variation on string 1 that a lot of people do.
c.:l: c. c.:h:
There is a problem with this string. On hit, the c.:h: whiffs on Arthur, Firebrand, Modok, Rocket Raccoon, Tron, and Wolverine.
String 3
A more advanced attack string that works on the whole cast on hit but only half the cast on block is:
c.:l: c. s.:h:
on hit, :d: :db: 
+:m:
on block you can do the same things as with string 1
If string 3 works on your opponent you should use it since it confirms into a higher damage combo.
This string works on:
Captain America, Chun-Li, Dante, Doctor Doom, Doctor Strange, Dormammu, Ghost Rider, Haggar, Hulk, Iron Fist, Iron Man, MODOK, Nemesis, Phoenix Wright, Sentinel, She-Hulk, Spencer, Strider, Super Skrull, Taskmaster, Thor, Tron, Vergil, Viewtiful Joe, and Wesker
It doesn’t work on block on the following characters (the s.H whiffs, leaving a gap where Deadpool can be hit/thrown):
Akuma, Amaterasu, Arthur, C. Viper, Chris, Deadpool, Felicia, Firebrand, Frank West, Hawkeye, Hsien-Ko, Jill, Magneto, Morrigan, Nova, Phoenix, Rocket Raccoon, Ryu, Shuma-Gorath, Spider-Man, Storm, Trish, Wolverine, X-23, and Zero
