Torsten Slok, chief international economist at Deutsche Bank, has listed all the risks to look out for with the markets in 2019.

And his list goes to 30.

Investors already have plenty to worry about — from the Federal Reserve's monetary policy to an extended government shutdown to the trade war with China — some of which have been weighing on the markets for months. After this week's pounding, the S&P 500 is now down 6 percent for the year and nearing a bear market.

"1. Algo-driven, risk parity fire sale in equities and credit continues"

First on Slok's list of worries is algorithmic trading, which has been criticized for triggering massive equity sell-offs and exacerbating volatility during market swings. More and more market transactions are now made through computerized trading that uses advanced mathematical models to make high-speed trading decisions. Some fear that the growing number of pre-set orders guided by only technical mechanics can completely gyrate the markets. Leon Cooperman raised this fear this week.

"10. U.S. 2s10s yield curve inversion has negative impact on confidence in credit and equity markets."

Slok is also worried that a recession indicator from the bond market will have negative impact on investor confidence.

The so-called yield curve inversion, a phenomenon characterized by short-term rates that exceed long-term rates, is getting close as the year comes to a close.

"11. U.S. corporate tax cuts continue to boost buybacks but not capex."

It's been a record year for stock buybacks but that didn't translate into stock gains.

"29. Fed and ECB restart QE and risky assets don't rally."

And consider this worst case scenario: the U.S. and global economy worsen to the point where the central banks have to restart quantitative easing — balance sheet expansion — and yet the markets respond by dropping further.

—CNBC's Michael Bloom contributed reporting.