Is there a way in Master Controller for a sim to achieve their LTW? My game is bugged and my sim has done everything necessary to achieve his LTW but it's not completing.

Not exactly. Which LTW is it? For some of them, this command might be helpful:
NRaas > MC > (Sim) > Advanced > Lifetime Wish:Change Tally (MC Cheats module required)

Another option is to use MC to change their LTW to something else, one that is easily fulfilled. With the addition of EPs and custom content over the years, some of them like learning 28 recipes or whatever it is have become trivial. Or you could use MC to grant them a packload of Happiness points, if those are what you are after. Doesn't quite "feel" the same as fulfillment, though.

It is the Master Romancer LTW, woohoo with 5 sims in different places. I have read that there is a problem with this one being badly bugged though. I have had a look at the tally options and played around with some numbers, but I don't think it's going to work with this one.
Yes it's more about the fulfilment rather than the points so I might have to change to a similar LTW.