@techNerd
Based on yoru example, you can actually modify your XML using the ReplaceText [1] processor.
The processor can be configured with Java regex that would match on the string you want to remove and the replacement value would be set to an empty string.

Your regex pattern in this case would need to match on (don't forget the spaces):
( unit = ".*?")
The parenthesis mark the java regex capture group.
.*? is a non greedy match on any character for zero or more characters until the very next quote. This allows this to match on any variety of unit strings ( meter, kilogram, and lb) from your example
This will result in the following:
<particular>
<name>Nicholas</name>
<height unit = "meter">183</height>
<weight unit = "kilogram" unit = "lb">75</weight>
</particular>
<particular>
<name>Debbie</name>
<height unit = "meter">163</height>
<weight unit = "kilogram" unit = "lb">45</weight>
</particular>
being converted to:
<particular>
<name>Nicholas</name>
<height>183</height>
<weight>75</weight>
</particular>
<particular>
<name>Debbie</name>
<height>163</height>
<weight>45</weight>
</particular>
[1] https://nifi.apache.org/docs/nifi-docs/components/org.apache.nifi/nifi-standard-nar/1.13.2/org.apache.nifi.processors.standard.ReplaceText/index.html
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Thank you,
Matt