With formal writing
Should we keep or omit "that"? or Is it optional?
Is there anything (that) happened (that) you particularly remember?
With formal writing
Should we keep or omit "that"? or Is it optional?
Is there anything (that) happened (that) you particularly remember?
The first "that" is obligatory because it is the subject of the relative clause "that happened."
The second "that" is not obligatory because it is not the subject of the relative clause "that you particularly remember." However, considering the presence of the first relative clause between the referent "anything" and the second relative clause, using the second "that" might be particularly advisable in writing.
You can read some theory and examples below for further reference (source: Swan's Practical English Usage):