Assuming that you don't want to just replicate that exact sound in the exact position of the video.
- Guitar tone control, attenuate/cut the highs
- Guitar volume control (manual swell)
- Volume pedal (manual swell)
- EQ pedal, attenuate/cut the highs
- Amp EQ / tone control, attenuate/cut the highs
- "Slow attack" or "swell" effects on various multi-effect and standalone pedals
- EHX Attack Decay, Pigtronix ADSR
- Compressor, gate, overdrive, EQ, attenuate/cut the highs
- Guitar synths (Roland VG, Boss SY, EHX Syn9, Line6 Helix)
- Guitar to MIDI converter and synth (Roland GR series, Jam Origin MIDI Guitar 2, Fishman Triple Play)
- Hex distortion/fuzz effects
- Reverbs even ... with 100% wet signal. And reverse reverb and delay.
- Jam Origin MIDI Guitar 2's "Deep Expressor" effect, where you can set the balance between attack and sustain components.
Search Youtube for "slow attack" and "swell". People are achieving this expression with many combinations of different effects, and you'll find many brands and models of effects.
The EHX Attack Decay is on my bucket list. It combines several of the needed tricks, without being an outright synth
Some effects are hard to categorize, like DSP things which split the signal to components and recombine them in various ways - is it a synth, is it an effect, what is it. Then there's things like the EHX Superego, which give you a "guitar sustain pedal" but also tools for melodic playing.