check
let
set
work
100

make sure that there is nothing wrong with someone / something

check on

100

fail to support or help someone as they had hoped

let down

100

establish a business

set up

100

try hard to improve or achieve something

work on

200

look at or take notice of 

check out

200

punish someone lightly or not at all

let off

200

to make someone or something different/special

set apart

200

find the answer to something

work out

300

tick or otherwise mark an item on a list to show that it has been dealt with

check off

300

(of something undesirable) becoming less intense

let up

300

cause a series of things to occur

set off

300

make somebody or yourself reach a state of great excitement/anger

work up