The phrase "huge disservice" means that a person or action has done something very unfair or harmful that negatively affects someone or a group of people. Full definition
The behaviour of the Lords is damaging for trust in democracy and does huge disservice to the standing and legitimacy of the mother of all parliaments. (theguardian.com)
It's in a parent's nature to want to protect your children from the slings and arrows of life, but take this too far and you'll do your precious offspring a huge disservice, warns mother of three Jen Brown. (inc.com)
But if you're not including outbound marketing tactics to your overall sales and marketing strategy, you're doing a huge disservice to your company and a bigger (discoverorg.com)