For example: selective enforcement, for example states vs terrorists. Even Russia became a victim of that, which I'll point out in hopes of avoiding discussion on Israel.
Russia, of course commits human rights abuses in Ukraine. But Daesh committed serious human rights abuses against Russia [1] [2], as did a number of other islamist, nationalist and even a socialist group. Not one iota of attention of the court ever went to that.
But this is a general problem. The court undertakes action against states, especially if they are currently unpopular in the UN (who appoints the judges), but never against the many groups that commit large scale human rights abuses against those states.
A third problem is that ICC convictions are entirely optional if you're in power. Any government is allowed to ask the ICC to not sue anyone for things either they did, or that happened on their soil. Sorry, any government EXCEPT the US and Israel are allowed to ask that. The ICC changed it's own statutes TWICE last year to sue Israel, and has done so before against the US. A relevant question would be "is the ICC allowed to change it's own statutes?" ... and of course the answer is no.
Or you could point out less serious, but ubiquitous human rights abuses that the ICC won't touch for various reasons. For example, every last muslim-majority state violates freedom of religion, a human right. Even Morocco and Turkey do [3] [4]. You will not hear the ICC on this issue.
Or to focus on a different problem, there's constant human rights abuses essentially everywhere on the planet in the prison system, including juvenile justice systems and just general youth services. This happens everywhere, with famous incidents in Romania, the US, France, Australia, ... you will not hear the ICC on this.
[1] https://en.wikipedia.org/wiki/Crocus_City_Hall_attack
[2] https://en.wikipedia.org/wiki/Beslan_school_siege
[3] https://en.wikipedia.org/wiki/Freedom_of_religion_in_Morocco
[4] https://en.wikipedia.org/wiki/Freedom_of_religion_in_Turkey#...