The obvious refactoring is to split the function up into smaller pieces, even if you can split it into two 1500 line functions that is a win.
Tell your manager that you want to refactor it. Just don't tell your manager "it's shit".
The "don't say it's shit" was when speaking to the manager... not using it on your thread. Unless I'm the one misunderstanding the statement...
ForAll(x): Shit(x)