DELETE

delete till end of file
dG

some other delete commands

added:
:g/^$/d
delete all (global) lines that have nothing from start (^) to end ($) i.e. blank or empty lines

:.,$d
delete lines from current line (.) to end of file ($)
dG will do the same. It's not an editor command so should be done directly on the line.

between marks
:'p,'qd
delete lines starting from mark p to mark q, including both p and q

delete current line and lines below
4dd
delete current line and 3 below it

delete current line and lines above it
3k4dd
3k moves the cursor 3 lines up and 4 dd deletes the required 4 lines