The component is declared by more than one NgModule

If you use your component in multiple modules, it means that this component is shared.
You need to create an exclusive module (ExampleModule) for your ExampleComponent, and then import that module wherever you want to use ExampleComponent.

So create ExampleModule:

import { NgModule } from '@angular/core';
import { ExampleComponent} from '../Example/Example.component';
@NgModule({
  declarations: [
    ExampleComponent,
  ],
  exports: [
    ExampleComponent,
  ]
})
export class ExampleModule { }

And then import it where you want to use ExampleComponent (into abc module and app module) like that:

import { ExampleModule } from '../example.module';
@NgModule({
  imports: [
    ExampleModule 
  ]
  ...
})

By defining separate module for your shared component, you provide some encapsulation layer in which you can describe and provide all the needed dependencies for your component to work, so, in the future, all the consumers just need to import the module itself without need to know any information about all these dependencies.