Very partial answer, from the South Korean experience:
The rapid spread of COVID-19 in South Korea has been attributed to one case linked to a superspreading event that has led to more than 3900 secondary cases stemming from church services in the city of Daegu (Kuhn, 2020; Ryall, 2020). This has led to sustained transmission chains of COVID-19, with 55% of the cases associated with the church cluster in Daegu (Bostock, 2020).
Moreover, three other clusters have been reported, including one set in Chundo Daenam hospital in Chungdo-gun, Gyeongsanggbuk-do (118 cases), one set in the gym in Cheonan, Chungcheongnam-do (92 cases), and one Pilgrimage to Israel cluster in Gyeongsanggbuk-do (49 cases). These few clusters have become the primary driving force of the infection.
The paper has more details on each cluster.
Similar patterns of large gatherings followed by spreading in families have been reported elsewhere, e.g. France and Italy. But most such studies published insofar focus on the early days of the pandemic, before the lockdowns were imposed.
Alas, for a more topical answer, it depends what one means by "hardcore" lockdowns. There is one such study being conducted in the German hotspot in Heinsberg. Insofar there have been only press interviews with the investigators, like
Instead, claims Streeck, his study found that: "There is no significant risk of catching the disease when you go shopping. Severe outbreaks of the infection were always a result of people being closer together over a longer period of time."
And as a reminder for what "hardcore" lockdowns actually means:
During the height of the lockdown, Wuhan residents were completely barred from stepping outside of their home, not even allowed to go grocery shopping and they were consequently completely reliant on designated neighborhood committees who delivered daily necessities to them.
Basically more or less home arrest for almost everyone.