The S&P 500 (SPX) decline from the 04/18/23 top is choppy, possibly an Elliott wave – Double Zigzag. If so there are two Fibonacci coordinates that indicate a support level that could be reached on 04/21/22.
The SPX – 30 – minute chart courtesy of Trading View shows where a bottom could be made.

The prime Fibonacci coordinate is from the SPX 03/24/23 bottom to the 04/18/23 top. A Fibonacci .236 retracement of the rally is at 4,108.06.
The secondary Fibonacci coordinate is from the 04/06/23 bottom to the 04/18/23 peak. A Fibonacci .618 retracement of this rally is at 4,107.81.
When you have two Fibonacci coordinates that are very close together it represents powerful support/resistance. A break trough of powerful support/resistance would require powerful force.
The 30 – minute RSI has so far reached 31.49%, the oversold boundary is at 30%. It’s possible an SPX bottom could be made with the RSI in the oversold zone. Or perhaps outside the oversold zone with an RSI bullish divergence. The best momentum evidence would be a bullish RSI divergence in the oversold zone.