1.
If you say that an activity or relationship is one-sided , you think that one of the people or groups involved does much more than the other or is much stronger than the other.
The negotiating was completely one-sided...
ADJ
2.
If you describe someone as one-sided , you are critical of what they say or do because you think it shows that they have considered only one side of an issue or event.
There has been a very one-sided account of her problems with Ted.
= biased
ADJ [ disapproval ]