缓解 vs. 缓和 - are the true synonyms/同义词?
Funnily enough《规范》has a note on its entry for 缓解 that says:


  注意 跟“缓和”不同。“缓解”侧重指“减轻”或“使减轻”; “缓和”侧重指“平和”或“使平和”。


A rough translation:

Note: it is different from “缓和”. “缓解” emphasizes alleviation or mitigation; “缓和” highlights “calming” or  “mildness.”

Oxford provides some examples that we can compare:


  缓解食品短缺状况 
  alleviate the food shortage 
  
  缓解痛苦 
  allay a pain 


and


  缓和紧张局势 
  relax the tension 
  
  形势有所缓和。 
  Things have eased up a bit.