Ok, all of these are similar and related. But there are some nuances...
First: JV does not necessarily mean M&A - so some risks pertaining to M&A (getting to that later) will not apply to JVs
M&A risks I would call those directly related to the transaction. There could be myriads:
- No shareholder approval
- Financing falls apart
- Regulatory / anti-trust approval is withheld or comes with very strict obligations (i.e. to divest a certain business, see Bayer <> Monsanto deal)
- Change of control clauses in key supplier or customer contracts
- No sufficient take rate for the acquisition offer to achieve a squeeze-out
- In the case of (hostile) acquisitions, some poison pill move by the acquired company
- Insufficient due diligence, so you buy at a high price due to some skeletons in the closet (pending class action lawsuits, some wrongdoing, ...)
Synergy risks I would characterize as those risks to achieving the projected synergies that ultimately justify the acquisition price:
- Longer / more expensive integration of organisations, systems etc.
- Key people leaving
- People not leaving / more expensive lay-offs
- Key customers leaving / shifting their buying strategy (i.e. because they don't want to be dependent on a single supplier)
- Better bargaining position towards customers or suppliers does not materialize
- Culture Clash
JV risks are similar in flavour to both (some related to the transaction, such as anti-trust) and some related to the operation of the joint company. I'd add a few more:
- Governance: Decision making slow / unclear due to shareholder involvement
- Intellectual property transfer (see China JVs)
- No equal contribution from JV partners...
- Your people don't want to work for the JV
- Balance sheet consolidation: If it was a goal to get a certain business off your balance sheet (financing at-equity) then that may not happen if you set up the JV wrong / don't find a suitable partner
There are tons more, but these are some examples.