I find it a bit misleading to focus on retractions. Articles being retracted is a necessary thing, and there is nothing more suspicious than a place that never retracted anything.
What matters here is obviously the nature of the retractions, the source of the problem, which generally means whether it's a fraud or not.
Exactly. If the author retracts an article, I could see that they're honest about themselves and probably just did something wrong, whilst journal retraction is deifnitely a red flag