‘Justify’ and ‘justification’ are powerful academic words and therefore excellent to use in formal essays.
Vocabulary takeaways
guarantee
Using expression to question how much can be guaranteed (e.g. websites that guarantee Band 7) shows critical thinking – see how to use it here.
in case of
‘In case of’ might not have the meaning you think it has – see the issues it causes here.
consideration
‘Consideration needs to be given to’ is such a nice formal expression that you can apply to many different topics.
benefit
There are many useful collocations for ‘benefit’ that will strengthen your arguments. Practise them here.
advent
‘Advent’ means ‘the coming of’, so it’s useful for introducting Task 2 essays e.g. ‘With the advent of the internet…’
trouble vs problem
The main difference between a problem and trouble is countable/uncountable.

on the contrary vs in contrast
Avoid using ‘on the contrary’ as a linking word – it is only used in very specific circumstances.
accommodation
Collocations with ‘accommodation’.