The best replacement for dethatcher is power rake.

The best alternatives to dethatcher are rated as following:
★★★★★  power rake
★★★★★  aerator
★★★★  tiller
★★★  rake
★★  overseeder
★  verticutter
★  scarifier

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Speaking about dethatcher, one probably shouldn't forget about sweeper.

Other search terms related to dethatcher and their ratings are:
★★★★★ sweeper
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Google Trends

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dethatcher
power rake
aerator